MySQL/MariaDB數據庫的多表查詢操做
MySQL/MariaDB數據庫的多表查詢操做html
做者：尹正傑node
版權聲明：原創做品，謝絕轉載！不然將追究法律責任。mysql
一.單表查詢小試牛刀sql
[root@node105.yinzhengjie.org.cn ~]# cat yinzhengjie_innodb.sql -- MySQL dump 10.13 Distrib 5.5.33, for Linux (x86_64) -- -- Host: localhost Database: yinzhengjie -- ------------------------------------------------------ -- Server version 5.5.33-log /*!40101 SET @OLD_CHARACTER_SET_CLIENT=@@CHARACTER_SET_CLIENT */; /*!40101 SET @OLD_CHARACTER_SET_RESULTS=@@CHARACTER_SET_RESULTS */; /*!40101 SET @OLD_COLLATION_CONNECTION=@@COLLATION_CONNECTION */; /*!40101 SET NAMES utf8 */; /*!40103 SET @OLD_TIME_ZONE=@@TIME_ZONE */; /*!40103 SET TIME_ZONE='+00:00' */; /*!40014 SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0 */; /*!40014 SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0 */; /*!40101 SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE='NO_AUTO_VALUE_ON_ZERO' */; /*!40111 SET @OLD_SQL_NOTES=@@SQL_NOTES, SQL_NOTES=0 */; -- -- Current Database: `yinzhengjie` -- CREATE DATABASE /*!32312 IF NOT EXISTS*/ `yinzhengjie` /*!40100 DEFAULT CHARACTER SET utf8 */; USE `yinzhengjie`; -- -- Table structure for table `classes` -- DROP TABLE IF EXISTS `classes`; /*!40101 SET @saved_cs_client = @@character_set_client */; /*!40101 SET character_set_client = utf8 */; CREATE TABLE `classes` ( `ClassID` tinyint(3) unsigned NOT NULL AUTO_INCREMENT, `Class` varchar(100) DEFAULT NULL, `NumOfStu` smallint(5) unsigned DEFAULT NULL, PRIMARY KEY (`ClassID`) ) ENGINE=InnoDB AUTO_INCREMENT=9 DEFAULT CHARSET=utf8; /*!40101 SET character_set_client = @saved_cs_client */; -- -- Dumping data for table `classes` -- LOCK TABLES `classes` WRITE; /*!40000 ALTER TABLE `classes` DISABLE KEYS */; INSERT INTO `classes` VALUES (1,'Shaolin Pai',10),(2,'Emei Pai',7),(3,'QingCheng Pai',11),(4,'Wudang Pai',12),(5,'Riyue Shenjiao',31),(6,'Liansha n Pai',27),(7,'Ming Jiao',27),(8,'Xiaoyao Pai',15);/*!40000 ALTER TABLE `classes` ENABLE KEYS */; UNLOCK TABLES; -- -- Table structure for table `coc` -- DROP TABLE IF EXISTS `coc`; /*!40101 SET @saved_cs_client = @@character_set_client */; /*!40101 SET character_set_client = utf8 */; CREATE TABLE `coc` ( `ID` int(10) unsigned NOT NULL AUTO_INCREMENT, `ClassID` tinyint(3) unsigned NOT NULL, `CourseID` smallint(5) unsigned DEFAULT NULL, PRIMARY KEY (`ID`) ) ENGINE=InnoDB AUTO_INCREMENT=15 DEFAULT CHARSET=utf8; /*!40101 SET character_set_client = @saved_cs_client */; -- -- Dumping data for table `coc` -- LOCK TABLES `coc` WRITE; /*!40000 ALTER TABLE `coc` DISABLE KEYS */; INSERT INTO `coc` VALUES (1,1,2),(2,1,5),(3,2,2),(4,2,6),(5,3,1),(6,3,7),(7,4,5),(8,4,2),(9,5,1),(10,5,9),(11,6,3),(12,6,4),(13,7,4),(14,7,3); /*!40000 ALTER TABLE `coc` ENABLE KEYS */; UNLOCK TABLES; -- -- Table structure for table `courses` -- DROP TABLE IF EXISTS `courses`; /*!40101 SET @saved_cs_client = @@character_set_client */; /*!40101 SET character_set_client = utf8 */; CREATE TABLE `courses` ( `CourseID` smallint(5) unsigned NOT NULL AUTO_INCREMENT, `Course` varchar(100) NOT NULL, PRIMARY KEY (`CourseID`) ) ENGINE=InnoDB AUTO_INCREMENT=8 DEFAULT CHARSET=utf8; /*!40101 SET character_set_client = @saved_cs_client */; -- -- Dumping data for table `courses` -- LOCK TABLES `courses` WRITE; /*!40000 ALTER TABLE `courses` DISABLE KEYS */; INSERT INTO `courses` VALUES (1,'Hamo Gong'),(2,'Kuihua Baodian'),(3,'Jinshe Jianfa'),(4,'Taiji Quan'),(5,'Daiyu Zanghua'),(6,'Weituo Zhang'),(7, 'Dagou Bangfa');/*!40000 ALTER TABLE `courses` ENABLE KEYS */; UNLOCK TABLES; -- -- Table structure for table `scores` -- DROP TABLE IF EXISTS `scores`; /*!40101 SET @saved_cs_client = @@character_set_client */; /*!40101 SET character_set_client = utf8 */; CREATE TABLE `scores` ( `ID` int(10) unsigned NOT NULL AUTO_INCREMENT, `StuID` int(10) unsigned NOT NULL, `CourseID` smallint(5) unsigned NOT NULL, `Score` tinyint(3) unsigned DEFAULT NULL, PRIMARY KEY (`ID`) ) ENGINE=InnoDB AUTO_INCREMENT=16 DEFAULT CHARSET=utf8; /*!40101 SET character_set_client = @saved_cs_client */; -- -- Dumping data for table `scores` -- LOCK TABLES `scores` WRITE; /*!40000 ALTER TABLE `scores` DISABLE KEYS */; INSERT INTO `scores` VALUES (1,1,2,77),(2,1,6,93),(3,2,2,47),(4,2,5,97),(5,3,2,88),(6,3,6,75),(7,4,5,71),(8,4,2,89),(9,5,1,39),(10,5,7,63),(11,6, 1,96),(12,7,1,86),(13,7,7,83),(14,8,4,57),(15,8,3,93);/*!40000 ALTER TABLE `scores` ENABLE KEYS */; UNLOCK TABLES; -- -- Table structure for table `students` -- DROP TABLE IF EXISTS `students`; /*!40101 SET @saved_cs_client = @@character_set_client */; /*!40101 SET character_set_client = utf8 */; CREATE TABLE `students` ( `StuID` int(10) unsigned NOT NULL AUTO_INCREMENT, `Name` varchar(50) NOT NULL, `Age` tinyint(3) unsigned NOT NULL, `Gender` enum('F','M') NOT NULL, `ClassID` tinyint(3) unsigned DEFAULT NULL, `TeacherID` int(10) unsigned DEFAULT NULL, PRIMARY KEY (`StuID`) ) ENGINE=InnoDB AUTO_INCREMENT=26 DEFAULT CHARSET=utf8; /*!40101 SET character_set_client = @saved_cs_client */; -- -- Dumping data for table `students` -- LOCK TABLES `students` WRITE; /*!40000 ALTER TABLE `students` DISABLE KEYS */; INSERT INTO `students` VALUES (1,'Shi Zhongyu',22,'M',2,3),(2,'Shi Potian',22,'M',1,7),(3,'Xie Yanke',53,'M',2,16),(4,'Ding Dian',32,'M',4,4),(5, 'Yu Yutong',26,'M',3,1),(6,'Shi Qing',46,'M',5,NULL),(7,'Xi Ren',19,'F',3,NULL),(8,'Lin Daiyu',17,'F',7,NULL),(9,'Ren Yingying',20,'F',6,NULL),(10,'Yue Lingshan',19,'F',3,NULL),(11,'Yuan Chengzhi',23,'M',6,NULL),(12,'Wen Qingqing',19,'F',1,NULL),(13,'Tian Boguang',33,'M',2,NULL),(14,'Lu Wushuang',17,'F',3,NULL),(15,'Duan Yu',19,'M',4,NULL),(16,'Xu Zhu',21,'M',1,NULL),(17,'Lin Chong',25,'M',4,NULL),(18,'Hua Rong',23,'M',7,NULL),(19,'Xue Baochai',18,'F',6,NULL),(20,'Diao Chan',19,'F',7,NULL),(21,'Huang Yueying',22,'F',6,NULL),(22,'Xiao Qiao',20,'F',1,NULL),(23,'Ma Chao',23,'M',4,NULL),(24,'Xu Xian',27,'M',NULL,NULL),(25,'Sun Dasheng',100,'M',NULL,NULL);/*!40000 ALTER TABLE `students` ENABLE KEYS */; UNLOCK TABLES; -- -- Table structure for table `teachers` -- DROP TABLE IF EXISTS `teachers`; /*!40101 SET @saved_cs_client = @@character_set_client */; /*!40101 SET character_set_client = utf8 */; CREATE TABLE `teachers` ( `TID` smallint(5) unsigned NOT NULL AUTO_INCREMENT, `Name` varchar(100) NOT NULL, `Age` tinyint(3) unsigned NOT NULL, `Gender` enum('F','M') DEFAULT NULL, PRIMARY KEY (`TID`) ) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8; /*!40101 SET character_set_client = @saved_cs_client */; -- -- Dumping data for table `teachers` -- LOCK TABLES `teachers` WRITE; /*!40000 ALTER TABLE `teachers` DISABLE KEYS */; INSERT INTO `teachers` VALUES (1,'Song Jiang',45,'M'),(2,'Zhang Sanfeng',94,'M'),(3,'Miejue Shitai',77,'F'),(4,'Lin Chaoying',93,'F'); /*!40000 ALTER TABLE `teachers` ENABLE KEYS */; UNLOCK TABLES; -- -- Table structure for table `toc` -- DROP TABLE IF EXISTS `toc`; /*!40101 SET @saved_cs_client = @@character_set_client */; /*!40101 SET character_set_client = utf8 */; CREATE TABLE `toc` ( `ID` int(10) unsigned NOT NULL AUTO_INCREMENT, `CourseID` smallint(5) unsigned DEFAULT NULL, `TID` smallint(5) unsigned DEFAULT NULL, PRIMARY KEY (`ID`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8; /*!40101 SET character_set_client = @saved_cs_client */; -- -- Dumping data for table `toc` -- LOCK TABLES `toc` WRITE; /*!40000 ALTER TABLE `toc` DISABLE KEYS */; /*!40000 ALTER TABLE `toc` ENABLE KEYS */; UNLOCK TABLES; /*!40103 SET TIME_ZONE=@OLD_TIME_ZONE */; /*!40101 SET SQL_MODE=@OLD_SQL_MODE */; /*!40014 SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS */; /*!40014 SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS */; /*!40101 SET CHARACTER_SET_CLIENT=@OLD_CHARACTER_SET_CLIENT */; /*!40101 SET CHARACTER_SET_RESULTS=@OLD_CHARACTER_SET_RESULTS */; /*!40101 SET COLLATION_CONNECTION=@OLD_COLLATION_CONNECTION */; /*!40111 SET SQL_NOTES=@OLD_SQL_NOTES */; -- Dump completed on 2013-09-03 2:51:27 [root@node105.yinzhengjie.org.cn ~]#
導入yinzhengjie_innodb.sql生成數據庫及相應的測試表數據信息，而後完成下面問題。
[root@node105.yinzhengjie.org.cn ~]# mysql -uroot -pyinzhengjie -S /mysql/3306/socket/mysql.sock Welcome to the MariaDB monitor. Commands end with ; or \g. Your MariaDB connection id is 17 Server version: 10.2.19-MariaDB MariaDB Server Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement. MariaDB [(none)]> MariaDB [(none)]> show databases; +--------------------+ | Database | +--------------------+ | information_schema | | mysql | | performance_schema | +--------------------+ rows in set (0.00 sec) MariaDB [(none)]> MariaDB [(none)]> SOURCE yinzhengjie_innodb.sql Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 1 row affected (0.00 sec) Database changed Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 8 rows affected (0.01 sec) Records: 8 Duplicates: 0 Warnings: 0 Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 14 rows affected (0.00 sec) Records: 14 Duplicates: 0 Warnings: 0 Query OK, 0 rows affected (0.01 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 7 rows affected (0.00 sec) Records: 7 Duplicates: 0 Warnings: 0 Query OK, 0 rows affected (0.01 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 15 rows affected (0.00 sec) Records: 15 Duplicates: 0 Warnings: 0 Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.01 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 25 rows affected (0.00 sec) Records: 25 Duplicates: 0 Warnings: 0 Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.01 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 4 rows affected (0.00 sec) Records: 4 Duplicates: 0 Warnings: 0 Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]> SHOW DATABASES; +--------------------+ | Database | +--------------------+ | information_schema | | mysql | | performance_schema | | yinzhengjie | +--------------------+ 4 rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]> SHOW TABLES; +-----------------------+ | Tables_in_yinzhengjie | +-----------------------+ | classes | | coc | | courses | | scores | | students | | teachers | | toc | +-----------------------+ 7 rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]>
1>.在students表中，查詢年齡大於25歲，且爲男性的同窗的名字和年齡數據庫
MariaDB [yinzhengjie]> SELECT * FROM students; +-------+---------------+-----+--------+---------+-----------+ | StuID | Name | Age | Gender | ClassID | TeacherID | +-------+---------------+-----+--------+---------+-----------+ | 1 | Shi Zhongyu | 22 | M | 2 | 3 | | 2 | Shi Potian | 22 | M | 1 | 7 | | 3 | Xie Yanke | 53 | M | 2 | 16 | | 4 | Ding Dian | 32 | M | 4 | 4 | | 5 | Yu Yutong | 26 | M | 3 | 1 | | 6 | Shi Qing | 46 | M | 5 | NULL | | 7 | Xi Ren | 19 | F | 3 | NULL | | 8 | Lin Daiyu | 17 | F | 7 | NULL | | 9 | Ren Yingying | 20 | F | 6 | NULL | | 10 | Yue Lingshan | 19 | F | 3 | NULL | | 11 | Yuan Chengzhi | 23 | M | 6 | NULL | | 12 | Wen Qingqing | 19 | F | 1 | NULL | | 13 | Tian Boguang | 33 | M | 2 | NULL | | 14 | Lu Wushuang | 17 | F | 3 | NULL | | 15 | Duan Yu | 19 | M | 4 | NULL | | 16 | Xu Zhu | 21 | M | 1 | NULL | | 17 | Lin Chong | 25 | M | 4 | NULL | | 18 | Hua Rong | 23 | M | 7 | NULL | | 19 | Xue Baochai | 18 | F | 6 | NULL | | 20 | Diao Chan | 19 | F | 7 | NULL | | 21 | Huang Yueying | 22 | F | 6 | NULL | | 22 | Xiao Qiao | 20 | F | 1 | NULL | | 23 | Ma Chao | 23 | M | 4 | NULL | | 24 | Xu Xian | 27 | M | NULL | NULL | | 25 | Sun Dasheng | 100 | M | NULL | NULL | +-------+---------------+-----+--------+---------+-----------+ 25 rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]> SELECT Name AS 姓名, Age AS 年齡 FROM students WHERE Age > 25 AND Gender = 'M'; +--------------+--------+ | 姓名 | 年齡 | +--------------+--------+ | Xie Yanke | 53 | | Ding Dian | 32 | | Yu Yutong | 26 | | Shi Qing | 46 | | Tian Boguang | 33 | | Xu Xian | 27 | | Sun Dasheng | 100 | +--------------+--------+ 7 rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]>
2>.以ClassID爲分組依據，顯示每組的平均年齡socket
MariaDB [yinzhengjie]> SELECT * FROM students; +-------+---------------+-----+--------+---------+-----------+ | StuID | Name | Age | Gender | ClassID | TeacherID | +-------+---------------+-----+--------+---------+-----------+ | 1 | Shi Zhongyu | 22 | M | 2 | 3 | | 2 | Shi Potian | 22 | M | 1 | 7 | | 3 | Xie Yanke | 53 | M | 2 | 16 | | 4 | Ding Dian | 32 | M | 4 | 4 | | 5 | Yu Yutong | 26 | M | 3 | 1 | | 6 | Shi Qing | 46 | M | 5 | NULL | | 7 | Xi Ren | 19 | F | 3 | NULL | | 8 | Lin Daiyu | 17 | F | 7 | NULL | | 9 | Ren Yingying | 20 | F | 6 | NULL | | 10 | Yue Lingshan | 19 | F | 3 | NULL | | 11 | Yuan Chengzhi | 23 | M | 6 | NULL | | 12 | Wen Qingqing | 19 | F | 1 | NULL | | 13 | Tian Boguang | 33 | M | 2 | NULL | | 14 | Lu Wushuang | 17 | F | 3 | NULL | | 15 | Duan Yu | 19 | M | 4 | NULL | | 16 | Xu Zhu | 21 | M | 1 | NULL | | 17 | Lin Chong | 25 | M | 4 | NULL | | 18 | Hua Rong | 23 | M | 7 | NULL | | 19 | Xue Baochai | 18 | F | 6 | NULL | | 20 | Diao Chan | 19 | F | 7 | NULL | | 21 | Huang Yueying | 22 | F | 6 | NULL | | 22 | Xiao Qiao | 20 | F | 1 | NULL | | 23 | Ma Chao | 23 | M | 4 | NULL | | 24 | Xu Xian | 27 | M | NULL | NULL | | 25 | Sun Dasheng | 100 | M | NULL | NULL | +-------+---------------+-----+--------+---------+-----------+ 25 rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]> SELECT ClassID,AVG(Age) FROM students GROUP BY ClassID; #查詢的結果NULL那一行始終在最上面 +---------+----------+ | ClassID | AVG(Age) | +---------+----------+ | NULL | 63.5000 | | 1 | 20.5000 | | 2 | 36.0000 | | 3 | 20.2500 | | 4 | 24.7500 | | 5 | 46.0000 | | 6 | 20.7500 | | 7 | 19.6667 | +---------+----------+ 8 rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]> SELECT ClassID,AVG(Age) FROM students GROUP BY -ClassID DESC; #能夠將NULL的結果放在最後一行輸出 +---------+----------+ | ClassID | AVG(Age) | +---------+----------+ | 1 | 20.5000 | | 2 | 36.0000 | | 3 | 20.2500 | | 4 | 24.7500 | | 5 | 46.0000 | | 6 | 20.7500 | | 7 | 19.6667 | | NULL | 63.5000 | +---------+----------+ 8 rows in set (0.00 sec) MariaDB [yinzhengjie]>
3>.顯示第2題中平均年齡大於30的分組及平均年齡ide
MariaDB [yinzhengjie]> SELECT * FROM students; +-------+---------------+-----+--------+---------+-----------+ | StuID | Name | Age | Gender | ClassID | TeacherID | +-------+---------------+-----+--------+---------+-----------+ | 1 | Shi Zhongyu | 22 | M | 2 | 3 | | 2 | Shi Potian | 22 | M | 1 | 7 | | 3 | Xie Yanke | 53 | M | 2 | 16 | | 4 | Ding Dian | 32 | M | 4 | 4 | | 5 | Yu Yutong | 26 | M | 3 | 1 | | 6 | Shi Qing | 46 | M | 5 | NULL | | 7 | Xi Ren | 19 | F | 3 | NULL | | 8 | Lin Daiyu | 17 | F | 7 | NULL | | 9 | Ren Yingying | 20 | F | 6 | NULL | | 10 | Yue Lingshan | 19 | F | 3 | NULL | | 11 | Yuan Chengzhi | 23 | M | 6 | NULL | | 12 | Wen Qingqing | 19 | F | 1 | NULL | | 13 | Tian Boguang | 33 | M | 2 | NULL | | 14 | Lu Wushuang | 17 | F | 3 | NULL | | 15 | Duan Yu | 19 | M | 4 | NULL | | 16 | Xu Zhu | 21 | M | 1 | NULL | | 17 | Lin Chong | 25 | M | 4 | NULL | | 18 | Hua Rong | 23 | M | 7 | NULL | | 19 | Xue Baochai | 18 | F | 6 | NULL | | 20 | Diao Chan | 19 | F | 7 | NULL | | 21 | Huang Yueying | 22 | F | 6 | NULL | | 22 | Xiao Qiao | 20 | F | 1 | NULL | | 23 | Ma Chao | 23 | M | 4 | NULL | | 24 | Xu Xian | 27 | M | NULL | NULL | | 25 | Sun Dasheng | 100 | M | NULL | NULL | +-------+---------------+-----+--------+---------+-----------+ 25 rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]> SELECT ClassID,AVG(Age) FROM students GROUP BY -ClassID DESC; +---------+----------+ | ClassID | AVG(Age) | +---------+----------+ | 1 | 20.5000 | | 2 | 36.0000 | | 3 | 20.2500 | | 4 | 24.7500 | | 5 | 46.0000 | | 6 | 20.7500 | | 7 | 19.6667 | | NULL | 63.5000 | +---------+----------+ 8 rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]> SELECT ClassID,AVG(Age) AS age FROM students GROUP BY -ClassID DESC HAVING age >30; +---------+---------+ | ClassID | age | +---------+---------+ | 2 | 36.0000 | | 5 | 46.0000 | | NULL | 63.5000 | +---------+---------+ 3 rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]>
4>.顯示以L開頭的名字的同窗的信息性能
MariaDB [yinzhengjie]> SELECT * FROM students; +-------+---------------+-----+--------+---------+-----------+ | StuID | Name | Age | Gender | ClassID | TeacherID | +-------+---------------+-----+--------+---------+-----------+ | 1 | Shi Zhongyu | 22 | M | 2 | 3 | | 2 | Shi Potian | 22 | M | 1 | 7 | | 3 | Xie Yanke | 53 | M | 2 | 16 | | 4 | Ding Dian | 32 | M | 4 | 4 | | 5 | Yu Yutong | 26 | M | 3 | 1 | | 6 | Shi Qing | 46 | M | 5 | NULL | | 7 | Xi Ren | 19 | F | 3 | NULL | | 8 | Lin Daiyu | 17 | F | 7 | NULL | | 9 | Ren Yingying | 20 | F | 6 | NULL | | 10 | Yue Lingshan | 19 | F | 3 | NULL | | 11 | Yuan Chengzhi | 23 | M | 6 | NULL | | 12 | Wen Qingqing | 19 | F | 1 | NULL | | 13 | Tian Boguang | 33 | M | 2 | NULL | | 14 | Lu Wushuang | 17 | F | 3 | NULL | | 15 | Duan Yu | 19 | M | 4 | NULL | | 16 | Xu Zhu | 21 | M | 1 | NULL | | 17 | Lin Chong | 25 | M | 4 | NULL | | 18 | Hua Rong | 23 | M | 7 | NULL | | 19 | Xue Baochai | 18 | F | 6 | NULL | | 20 | Diao Chan | 19 | F | 7 | NULL | | 21 | Huang Yueying | 22 | F | 6 | NULL | | 22 | Xiao Qiao | 20 | F | 1 | NULL | | 23 | Ma Chao | 23 | M | 4 | NULL | | 24 | Xu Xian | 27 | M | NULL | NULL | | 25 | Sun Dasheng | 100 | M | NULL | NULL | +-------+---------------+-----+--------+---------+-----------+ 25 rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]> SELECT * FROM students WHERE Name RLIKE '^L'; +-------+-------------+-----+--------+---------+-----------+ | StuID | Name | Age | Gender | ClassID | TeacherID | +-------+-------------+-----+--------+---------+-----------+ | 8 | Lin Daiyu | 17 | F | 7 | NULL | | 14 | Lu Wushuang | 17 | F | 3 | NULL | | 17 | Lin Chong | 25 | M | 4 | NULL | +-------+-------------+-----+--------+---------+-----------+ 3 rows in set (0.00 sec) MariaDB [yinzhengjie]>
5>.顯示TeacherID非空的同窗的相關信息學習
MariaDB [yinzhengjie]> SELECT * FROM students; +-------+---------------+-----+--------+---------+-----------+ | StuID | Name | Age | Gender | ClassID | TeacherID | +-------+---------------+-----+--------+---------+-----------+ | 1 | Shi Zhongyu | 22 | M | 2 | 3 | | 2 | Shi Potian | 22 | M | 1 | 7 | | 3 | Xie Yanke | 53 | M | 2 | 16 | | 4 | Ding Dian | 32 | M | 4 | 4 | | 5 | Yu Yutong | 26 | M | 3 | 1 | | 6 | Shi Qing | 46 | M | 5 | NULL | | 7 | Xi Ren | 19 | F | 3 | NULL | | 8 | Lin Daiyu | 17 | F | 7 | NULL | | 9 | Ren Yingying | 20 | F | 6 | NULL | | 10 | Yue Lingshan | 19 | F | 3 | NULL | | 11 | Yuan Chengzhi | 23 | M | 6 | NULL | | 12 | Wen Qingqing | 19 | F | 1 | NULL | | 13 | Tian Boguang | 33 | M | 2 | NULL | | 14 | Lu Wushuang | 17 | F | 3 | NULL | | 15 | Duan Yu | 19 | M | 4 | NULL | | 16 | Xu Zhu | 21 | M | 1 | NULL | | 17 | Lin Chong | 25 | M | 4 | NULL | | 18 | Hua Rong | 23 | M | 7 | NULL | | 19 | Xue Baochai | 18 | F | 6 | NULL | | 20 | Diao Chan | 19 | F | 7 | NULL | | 21 | Huang Yueying | 22 | F | 6 | NULL | | 22 | Xiao Qiao | 20 | F | 1 | NULL | | 23 | Ma Chao | 23 | M | 4 | NULL | | 24 | Xu Xian | 27 | M | NULL | NULL | | 25 | Sun Dasheng | 100 | M | NULL | NULL | +-------+---------------+-----+--------+---------+-----------+ 25 rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]> SELECT * FROM students WHERE TeacherID IS NOT NULL; +-------+-------------+-----+--------+---------+-----------+ | StuID | Name | Age | Gender | ClassID | TeacherID | +-------+-------------+-----+--------+---------+-----------+ | 1 | Shi Zhongyu | 22 | M | 2 | 3 | | 2 | Shi Potian | 22 | M | 1 | 7 | | 3 | Xie Yanke | 53 | M | 2 | 16 | | 4 | Ding Dian | 32 | M | 4 | 4 | | 5 | Yu Yutong | 26 | M | 3 | 1 | +-------+-------------+-----+--------+---------+-----------+ 5 rows in set (0.00 sec) MariaDB [yinzhengjie]>
6>.以年齡排序後，顯示年齡最大的前10位同窗的信息測試
MariaDB [yinzhengjie]> SELECT * FROM students; +-------+---------------+-----+--------+---------+-----------+ | StuID | Name | Age | Gender | ClassID | TeacherID | +-------+---------------+-----+--------+---------+-----------+ | 1 | Shi Zhongyu | 22 | M | 2 | 3 | | 2 | Shi Potian | 22 | M | 1 | 7 | | 3 | Xie Yanke | 53 | M | 2 | 16 | | 4 | Ding Dian | 32 | M | 4 | 4 | | 5 | Yu Yutong | 26 | M | 3 | 1 | | 6 | Shi Qing | 46 | M | 5 | NULL | | 7 | Xi Ren | 19 | F | 3 | NULL | | 8 | Lin Daiyu | 17 | F | 7 | NULL | | 9 | Ren Yingying | 20 | F | 6 | NULL | | 10 | Yue Lingshan | 19 | F | 3 | NULL | | 11 | Yuan Chengzhi | 23 | M | 6 | NULL | | 12 | Wen Qingqing | 19 | F | 1 | NULL | | 13 | Tian Boguang | 33 | M | 2 | NULL | | 14 | Lu Wushuang | 17 | F | 3 | NULL | | 15 | Duan Yu | 19 | M | 4 | NULL | | 16 | Xu Zhu | 21 | M | 1 | NULL | | 17 | Lin Chong | 25 | M | 4 | NULL | | 18 | Hua Rong | 23 | M | 7 | NULL | | 19 | Xue Baochai | 18 | F | 6 | NULL | | 20 | Diao Chan | 19 | F | 7 | NULL | | 21 | Huang Yueying | 22 | F | 6 | NULL | | 22 | Xiao Qiao | 20 | F | 1 | NULL | | 23 | Ma Chao | 23 | M | 4 | NULL | | 24 | Xu Xian | 27 | M | NULL | NULL | | 25 | Sun Dasheng | 100 | M | NULL | NULL | +-------+---------------+-----+--------+---------+-----------+ 25 rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]> SELECT * FROM students ORDER BY Age DESC LIMIT 10; +-------+--------------+-----+--------+---------+-----------+ | StuID | Name | Age | Gender | ClassID | TeacherID | +-------+--------------+-----+--------+---------+-----------+ | 25 | Sun Dasheng | 100 | M | NULL | NULL | | 3 | Xie Yanke | 53 | M | 2 | 16 | | 6 | Shi Qing | 46 | M | 5 | NULL | | 13 | Tian Boguang | 33 | M | 2 | NULL | | 4 | Ding Dian | 32 | M | 4 | 4 | | 24 | Xu Xian | 27 | M | NULL | NULL | | 5 | Yu Yutong | 26 | M | 3 | 1 | | 17 | Lin Chong | 25 | M | 4 | NULL | | 23 | Ma Chao | 23 | M | 4 | NULL | | 18 | Hua Rong | 23 | M | 7 | NULL | +-------+--------------+-----+--------+---------+-----------+ 10 rows in set (0.00 sec) MariaDB [yinzhengjie]>
7>.查詢年齡大於等於20歲，小於等於25歲的同窗的信息
MariaDB [yinzhengjie]> SELECT * FROM students; +-------+---------------+-----+--------+---------+-----------+ | StuID | Name | Age | Gender | ClassID | TeacherID | +-------+---------------+-----+--------+---------+-----------+ | 1 | Shi Zhongyu | 22 | M | 2 | 3 | | 2 | Shi Potian | 22 | M | 1 | 7 | | 3 | Xie Yanke | 53 | M | 2 | 16 | | 4 | Ding Dian | 32 | M | 4 | 4 | | 5 | Yu Yutong | 26 | M | 3 | 1 | | 6 | Shi Qing | 46 | M | 5 | NULL | | 7 | Xi Ren | 19 | F | 3 | NULL | | 8 | Lin Daiyu | 17 | F | 7 | NULL | | 9 | Ren Yingying | 20 | F | 6 | NULL | | 10 | Yue Lingshan | 19 | F | 3 | NULL | | 11 | Yuan Chengzhi | 23 | M | 6 | NULL | | 12 | Wen Qingqing | 19 | F | 1 | NULL | | 13 | Tian Boguang | 33 | M | 2 | NULL | | 14 | Lu Wushuang | 17 | F | 3 | NULL | | 15 | Duan Yu | 19 | M | 4 | NULL | | 16 | Xu Zhu | 21 | M | 1 | NULL | | 17 | Lin Chong | 25 | M | 4 | NULL | | 18 | Hua Rong | 23 | M | 7 | NULL | | 19 | Xue Baochai | 18 | F | 6 | NULL | | 20 | Diao Chan | 19 | F | 7 | NULL | | 21 | Huang Yueying | 22 | F | 6 | NULL | | 22 | Xiao Qiao | 20 | F | 1 | NULL | | 23 | Ma Chao | 23 | M | 4 | NULL | | 24 | Xu Xian | 27 | M | NULL | NULL | | 25 | Sun Dasheng | 100 | M | NULL | NULL | +-------+---------------+-----+--------+---------+-----------+ 25 rows in set (0.00 sec) MariaDB [yinzhengjie]> SELECT * FROM students WHERE Age BETWEEN 20 AND 25; +-------+---------------+-----+--------+---------+-----------+ | StuID | Name | Age | Gender | ClassID | TeacherID | +-------+---------------+-----+--------+---------+-----------+ | 1 | Shi Zhongyu | 22 | M | 2 | 3 | | 2 | Shi Potian | 22 | M | 1 | 7 | | 9 | Ren Yingying | 20 | F | 6 | NULL | | 11 | Yuan Chengzhi | 23 | M | 6 | NULL | | 16 | Xu Zhu | 21 | M | 1 | NULL | | 17 | Lin Chong | 25 | M | 4 | NULL | | 18 | Hua Rong | 23 | M | 7 | NULL | | 21 | Huang Yueying | 22 | F | 6 | NULL | | 22 | Xiao Qiao | 20 | F | 1 | NULL | | 23 | Ma Chao | 23 | M | 4 | NULL | +-------+---------------+-----+--------+---------+-----------+ 10 rows in set (0.00 sec) MariaDB [yinzhengjie]>
MariaDB [yinzhengjie]> SELECT * FROM students; +-------+---------------+-----+--------+---------+-----------+ | StuID | Name | Age | Gender | ClassID | TeacherID | +-------+---------------+-----+--------+---------+-----------+ | 1 | Shi Zhongyu | 22 | M | 2 | 3 | | 2 | Shi Potian | 22 | M | 1 | 7 | | 3 | Xie Yanke | 53 | M | 2 | 16 | | 4 | Ding Dian | 32 | M | 4 | 4 | | 5 | Yu Yutong | 26 | M | 3 | 1 | | 6 | Shi Qing | 46 | M | 5 | NULL | | 7 | Xi Ren | 19 | F | 3 | NULL | | 8 | Lin Daiyu | 17 | F | 7 | NULL | | 9 | Ren Yingying | 20 | F | 6 | NULL | | 10 | Yue Lingshan | 19 | F | 3 | NULL | | 11 | Yuan Chengzhi | 23 | M | 6 | NULL | | 12 | Wen Qingqing | 19 | F | 1 | NULL | | 13 | Tian Boguang | 33 | M | 2 | NULL | | 14 | Lu Wushuang | 17 | F | 3 | NULL | | 15 | Duan Yu | 19 | M | 4 | NULL | | 16 | Xu Zhu | 21 | M | 1 | NULL | | 17 | Lin Chong | 25 | M | 4 | NULL | | 18 | Hua Rong | 23 | M | 7 | NULL | | 19 | Xue Baochai | 18 | F | 6 | NULL | | 20 | Diao Chan | 19 | F | 7 | NULL | | 21 | Huang Yueying | 22 | F | 6 | NULL | | 22 | Xiao Qiao | 20 | F | 1 | NULL | | 23 | Ma Chao | 23 | M | 4 | NULL | | 24 | Xu Xian | 27 | M | NULL | NULL | | 25 | Sun Dasheng | 100 | M | NULL | NULL | +-------+---------------+-----+--------+---------+-----------+ 25 rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]> SELECT * FROM students WHERE Age >= 20 AND AGE <= 25; +-------+---------------+-----+--------+---------+-----------+ | StuID | Name | Age | Gender | ClassID | TeacherID | +-------+---------------+-----+--------+---------+-----------+ | 1 | Shi Zhongyu | 22 | M | 2 | 3 | | 2 | Shi Potian | 22 | M | 1 | 7 | | 9 | Ren Yingying | 20 | F | 6 | NULL | | 11 | Yuan Chengzhi | 23 | M | 6 | NULL | | 16 | Xu Zhu | 21 | M | 1 | NULL | | 17 | Lin Chong | 25 | M | 4 | NULL | | 18 | Hua Rong | 23 | M | 7 | NULL | | 21 | Huang Yueying | 22 | F | 6 | NULL | | 22 | Xiao Qiao | 20 | F | 1 | NULL | | 23 | Ma Chao | 23 | M | 4 | NULL | +-------+---------------+-----+--------+---------+-----------+ 10 rows in set (0.00 sec) MariaDB [yinzhengjie]>
二.多表查詢(基於上面導入的"yinzhengjie_innodb.sql"數據進行演示)
博主推薦閱讀: https://www.runoob.com/sql/sql-join.html
1>.將兩張表中個別字段聯合顯示(縱向合併)
聯合查詢：UNION 擁有自動去重的功能 兩張表中字段數量得相同 示例: SELECT Name,Age FROM students UNION SELECT Name,Age FROM teachers;
MariaDB [yinzhengjie]> SHOW TABLES; +-----------------------+ | Tables_in_yinzhengjie | +-----------------------+ | classes | | coc | | courses | | scores | | students | | teachers | | toc | +-----------------------+ 7 rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]> SELECT * FROM teachers; +-----+---------------+-----+--------+ | TID | Name | Age | Gender | +-----+---------------+-----+--------+ | 1 | Song Jiang | 45 | M | | 2 | Zhang Sanfeng | 94 | M | | 3 | Miejue Shitai | 77 | F | | 4 | Lin Chaoying | 93 | F | +-----+---------------+-----+--------+ 4 rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]> SELECT * FROM students; +-------+---------------+-----+--------+---------+-----------+ | StuID | Name | Age | Gender | ClassID | TeacherID | +-------+---------------+-----+--------+---------+-----------+ | 1 | Shi Zhongyu | 22 | M | 2 | 3 | | 2 | Shi Potian | 22 | M | 1 | 7 | | 3 | Xie Yanke | 53 | M | 2 | 16 | | 4 | Ding Dian | 32 | M | 4 | 4 | | 5 | Yu Yutong | 26 | M | 3 | 1 | | 6 | Shi Qing | 46 | M | 5 | NULL | | 7 | Xi Ren | 19 | F | 3 | NULL | | 8 | Lin Daiyu | 17 | F | 7 | NULL | | 9 | Ren Yingying | 20 | F | 6 | NULL | | 10 | Yue Lingshan | 19 | F | 3 | NULL | | 11 | Yuan Chengzhi | 23 | M | 6 | NULL | | 12 | Wen Qingqing | 19 | F | 1 | NULL | | 13 | Tian Boguang | 33 | M | 2 | NULL | | 14 | Lu Wushuang | 17 | F | 3 | NULL | | 15 | Duan Yu | 19 | M | 4 | NULL | | 16 | Xu Zhu | 21 | M | 1 | NULL | | 17 | Lin Chong | 25 | M | 4 | NULL | | 18 | Hua Rong | 23 | M | 7 | NULL | | 19 | Xue Baochai | 18 | F | 6 | NULL | | 20 | Diao Chan | 19 | F | 7 | NULL | | 21 | Huang Yueying | 22 | F | 6 | NULL | | 22 | Xiao Qiao | 20 | F | 1 | NULL | | 23 | Ma Chao | 23 | M | 4 | NULL | | 24 | Xu Xian | 27 | M | NULL | NULL | | 25 | Sun Dasheng | 100 | M | NULL | NULL | +-------+---------------+-----+--------+---------+-----------+ 25 rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]> SELECT StuID AS id ,Name AS 姓名 FROM students UNION SELECT TID,Name FROM teachers; +----+---------------+ | id | 姓名 | +----+---------------+ | 1 | Shi Zhongyu | | 2 | Shi Potian | | 3 | Xie Yanke | | 4 | Ding Dian | | 5 | Yu Yutong | | 6 | Shi Qing | | 7 | Xi Ren | | 8 | Lin Daiyu | | 9 | Ren Yingying | | 10 | Yue Lingshan | | 11 | Yuan Chengzhi | | 12 | Wen Qingqing | | 13 | Tian Boguang | | 14 | Lu Wushuang | | 15 | Duan Yu | | 16 | Xu Zhu | | 17 | Lin Chong | | 18 | Hua Rong | | 19 | Xue Baochai | | 20 | Diao Chan | | 21 | Huang Yueying | | 22 | Xiao Qiao | | 23 | Ma Chao | | 24 | Xu Xian | | 25 | Sun Dasheng | | 1 | Song Jiang | | 2 | Zhang Sanfeng | | 3 | Miejue Shitai | | 4 | Lin Chaoying | +----+---------------+ 29 rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]>
2>.笛卡爾乘積查詢(又稱交叉鏈接，橫向合併，生成環境應該避免這種查詢)
MariaDB [yinzhengjie]> SELECT * FROM students; +-------+---------------+-----+--------+---------+-----------+ | StuID | Name | Age | Gender | ClassID | TeacherID | +-------+---------------+-----+--------+---------+-----------+ | 1 | Shi Zhongyu | 22 | M | 2 | 3 | | 2 | Shi Potian | 22 | M | 1 | 7 | | 3 | Xie Yanke | 53 | M | 2 | 16 | | 4 | Ding Dian | 32 | M | 4 | 4 | | 5 | Yu Yutong | 26 | M | 3 | 1 | | 6 | Shi Qing | 46 | M | 5 | NULL | | 7 | Xi Ren | 19 | F | 3 | NULL | | 8 | Lin Daiyu | 17 | F | 7 | NULL | | 9 | Ren Yingying | 20 | F | 6 | NULL | | 10 | Yue Lingshan | 19 | F | 3 | NULL | | 11 | Yuan Chengzhi | 23 | M | 6 | NULL | | 12 | Wen Qingqing | 19 | F | 1 | NULL | | 13 | Tian Boguang | 33 | M | 2 | NULL | | 14 | Lu Wushuang | 17 | F | 3 | NULL | | 15 | Duan Yu | 19 | M | 4 | NULL | | 16 | Xu Zhu | 21 | M | 1 | NULL | | 17 | Lin Chong | 25 | M | 4 | NULL | | 18 | Hua Rong | 23 | M | 7 | NULL | | 19 | Xue Baochai | 18 | F | 6 | NULL | | 20 | Diao Chan | 19 | F | 7 | NULL | | 21 | Huang Yueying | 22 | F | 6 | NULL | | 22 | Xiao Qiao | 20 | F | 1 | NULL | | 23 | Ma Chao | 23 | M | 4 | NULL | | 24 | Xu Xian | 27 | M | NULL | NULL | | 25 | Sun Dasheng | 100 | M | NULL | NULL | +-------+---------------+-----+--------+---------+-----------+ 25 rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]> SELECT * FROM teachers; +-----+---------------+-----+--------+ | TID | Name | Age | Gender | +-----+---------------+-----+--------+ | 1 | Song Jiang | 45 | M | | 2 | Zhang Sanfeng | 94 | M | | 3 | Miejue Shitai | 77 | F | | 4 | Lin Chaoying | 93 | F | +-----+---------------+-----+--------+ 4 rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]> SELECT * FROM students CROSS JOIN teachers; #笛卡爾積查詢，生產環境應該避免這樣的查詢。 +-------+---------------+-----+--------+---------+-----------+-----+---------------+-----+--------+ | StuID | Name | Age | Gender | ClassID | TeacherID | TID | Name | Age | Gender | +-------+---------------+-----+--------+---------+-----------+-----+---------------+-----+--------+ | 1 | Shi Zhongyu | 22 | M | 2 | 3 | 1 | Song Jiang | 45 | M | | 1 | Shi Zhongyu | 22 | M | 2 | 3 | 2 | Zhang Sanfeng | 94 | M | | 1 | Shi Zhongyu | 22 | M | 2 | 3 | 3 | Miejue Shitai | 77 | F | | 1 | Shi Zhongyu | 22 | M | 2 | 3 | 4 | Lin Chaoying | 93 | F | | 2 | Shi Potian | 22 | M | 1 | 7 | 1 | Song Jiang | 45 | M | | 2 | Shi Potian | 22 | M | 1 | 7 | 2 | Zhang Sanfeng | 94 | M | | 2 | Shi Potian | 22 | M | 1 | 7 | 3 | Miejue Shitai | 77 | F | | 2 | Shi Potian | 22 | M | 1 | 7 | 4 | Lin Chaoying | 93 | F | | 3 | Xie Yanke | 53 | M | 2 | 16 | 1 | Song Jiang | 45 | M | | 3 | Xie Yanke | 53 | M | 2 | 16 | 2 | Zhang Sanfeng | 94 | M | | 3 | Xie Yanke | 53 | M | 2 | 16 | 3 | Miejue Shitai | 77 | F | | 3 | Xie Yanke | 53 | M | 2 | 16 | 4 | Lin Chaoying | 93 | F | | 4 | Ding Dian | 32 | M | 4 | 4 | 1 | Song Jiang | 45 | M | | 4 | Ding Dian | 32 | M | 4 | 4 | 2 | Zhang Sanfeng | 94 | M | | 4 | Ding Dian | 32 | M | 4 | 4 | 3 | Miejue Shitai | 77 | F | | 4 | Ding Dian | 32 | M | 4 | 4 | 4 | Lin Chaoying | 93 | F | | 5 | Yu Yutong | 26 | M | 3 | 1 | 1 | Song Jiang | 45 | M | | 5 | Yu Yutong | 26 | M | 3 | 1 | 2 | Zhang Sanfeng | 94 | M | | 5 | Yu Yutong | 26 | M | 3 | 1 | 3 | Miejue Shitai | 77 | F | | 5 | Yu Yutong | 26 | M | 3 | 1 | 4 | Lin Chaoying | 93 | F | | 6 | Shi Qing | 46 | M | 5 | NULL | 1 | Song Jiang | 45 | M | | 6 | Shi Qing | 46 | M | 5 | NULL | 2 | Zhang Sanfeng | 94 | M | | 6 | Shi Qing | 46 | M | 5 | NULL | 3 | Miejue Shitai | 77 | F | | 6 | Shi Qing | 46 | M | 5 | NULL | 4 | Lin Chaoying | 93 | F | | 7 | Xi Ren | 19 | F | 3 | NULL | 1 | Song Jiang | 45 | M | | 7 | Xi Ren | 19 | F | 3 | NULL | 2 | Zhang Sanfeng | 94 | M | | 7 | Xi Ren | 19 | F | 3 | NULL | 3 | Miejue Shitai | 77 | F | | 7 | Xi Ren | 19 | F | 3 | NULL | 4 | Lin Chaoying | 93 | F | | 8 | Lin Daiyu | 17 | F | 7 | NULL | 1 | Song Jiang | 45 | M | | 8 | Lin Daiyu | 17 | F | 7 | NULL | 2 | Zhang Sanfeng | 94 | M | | 8 | Lin Daiyu | 17 | F | 7 | NULL | 3 | Miejue Shitai | 77 | F | | 8 | Lin Daiyu | 17 | F | 7 | NULL | 4 | Lin Chaoying | 93 | F | | 9 | Ren Yingying | 20 | F | 6 | NULL | 1 | Song Jiang | 45 | M | | 9 | Ren Yingying | 20 | F | 6 | NULL | 2 | Zhang Sanfeng | 94 | M | | 9 | Ren Yingying | 20 | F | 6 | NULL | 3 | Miejue Shitai | 77 | F | | 9 | Ren Yingying | 20 | F | 6 | NULL | 4 | Lin Chaoying | 93 | F | | 10 | Yue Lingshan | 19 | F | 3 | NULL | 1 | Song Jiang | 45 | M | | 10 | Yue Lingshan | 19 | F | 3 | NULL | 2 | Zhang Sanfeng | 94 | M | | 10 | Yue Lingshan | 19 | F | 3 | NULL | 3 | Miejue Shitai | 77 | F | | 10 | Yue Lingshan | 19 | F | 3 | NULL | 4 | Lin Chaoying | 93 | F | | 11 | Yuan Chengzhi | 23 | M | 6 | NULL | 1 | Song Jiang | 45 | M | | 11 | Yuan Chengzhi | 23 | M | 6 | NULL | 2 | Zhang Sanfeng | 94 | M | | 11 | Yuan Chengzhi | 23 | M | 6 | NULL | 3 | Miejue Shitai | 77 | F | | 11 | Yuan Chengzhi | 23 | M | 6 | NULL | 4 | Lin Chaoying | 93 | F | | 12 | Wen Qingqing | 19 | F | 1 | NULL | 1 | Song Jiang | 45 | M | | 12 | Wen Qingqing | 19 | F | 1 | NULL | 2 | Zhang Sanfeng | 94 | M | | 12 | Wen Qingqing | 19 | F | 1 | NULL | 3 | Miejue Shitai | 77 | F | | 12 | Wen Qingqing | 19 | F | 1 | NULL | 4 | Lin Chaoying | 93 | F | | 13 | Tian Boguang | 33 | M | 2 | NULL | 1 | Song Jiang | 45 | M | | 13 | Tian Boguang | 33 | M | 2 | NULL | 2 | Zhang Sanfeng | 94 | M | | 13 | Tian Boguang | 33 | M | 2 | NULL | 3 | Miejue Shitai | 77 | F | | 13 | Tian Boguang | 33 | M | 2 | NULL | 4 | Lin Chaoying | 93 | F | | 14 | Lu Wushuang | 17 | F | 3 | NULL | 1 | Song Jiang | 45 | M | | 14 | Lu Wushuang | 17 | F | 3 | NULL | 2 | Zhang Sanfeng | 94 | M | | 14 | Lu Wushuang | 17 | F | 3 | NULL | 3 | Miejue Shitai | 77 | F | | 14 | Lu Wushuang | 17 | F | 3 | NULL | 4 | Lin Chaoying | 93 | F | | 15 | Duan Yu | 19 | M | 4 | NULL | 1 | Song Jiang | 45 | M | | 15 | Duan Yu | 19 | M | 4 | NULL | 2 | Zhang Sanfeng | 94 | M | | 15 | Duan Yu | 19 | M | 4 | NULL | 3 | Miejue Shitai | 77 | F | | 15 | Duan Yu | 19 | M | 4 | NULL | 4 | Lin Chaoying | 93 | F | | 16 | Xu Zhu | 21 | M | 1 | NULL | 1 | Song Jiang | 45 | M | | 16 | Xu Zhu | 21 | M | 1 | NULL | 2 | Zhang Sanfeng | 94 | M | | 16 | Xu Zhu | 21 | M | 1 | NULL | 3 | Miejue Shitai | 77 | F | | 16 | Xu Zhu | 21 | M | 1 | NULL | 4 | Lin Chaoying | 93 | F | | 17 | Lin Chong | 25 | M | 4 | NULL | 1 | Song Jiang | 45 | M | | 17 | Lin Chong | 25 | M | 4 | NULL | 2 | Zhang Sanfeng | 94 | M | | 17 | Lin Chong | 25 | M | 4 | NULL | 3 | Miejue Shitai | 77 | F | | 17 | Lin Chong | 25 | M | 4 | NULL | 4 | Lin Chaoying | 93 | F | | 18 | Hua Rong | 23 | M | 7 | NULL | 1 | Song Jiang | 45 | M | | 18 | Hua Rong | 23 | M | 7 | NULL | 2 | Zhang Sanfeng | 94 | M | | 18 | Hua Rong | 23 | M | 7 | NULL | 3 | Miejue Shitai | 77 | F | | 18 | Hua Rong | 23 | M | 7 | NULL | 4 | Lin Chaoying | 93 | F | | 19 | Xue Baochai | 18 | F | 6 | NULL | 1 | Song Jiang | 45 | M | | 19 | Xue Baochai | 18 | F | 6 | NULL | 2 | Zhang Sanfeng | 94 | M | | 19 | Xue Baochai | 18 | F | 6 | NULL | 3 | Miejue Shitai | 77 | F | | 19 | Xue Baochai | 18 | F | 6 | NULL | 4 | Lin Chaoying | 93 | F | | 20 | Diao Chan | 19 | F | 7 | NULL | 1 | Song Jiang | 45 | M | | 20 | Diao Chan | 19 | F | 7 | NULL | 2 | Zhang Sanfeng | 94 | M | | 20 | Diao Chan | 19 | F | 7 | NULL | 3 | Miejue Shitai | 77 | F | | 20 | Diao Chan | 19 | F | 7 | NULL | 4 | Lin Chaoying | 93 | F | | 21 | Huang Yueying | 22 | F | 6 | NULL | 1 | Song Jiang | 45 | M | | 21 | Huang Yueying | 22 | F | 6 | NULL | 2 | Zhang Sanfeng | 94 | M | | 21 | Huang Yueying | 22 | F | 6 | NULL | 3 | Miejue Shitai | 77 | F | | 21 | Huang Yueying | 22 | F | 6 | NULL | 4 | Lin Chaoying | 93 | F | | 22 | Xiao Qiao | 20 | F | 1 | NULL | 1 | Song Jiang | 45 | M | | 22 | Xiao Qiao | 20 | F | 1 | NULL | 2 | Zhang Sanfeng | 94 | M | | 22 | Xiao Qiao | 20 | F | 1 | NULL | 3 | Miejue Shitai | 77 | F | | 22 | Xiao Qiao | 20 | F | 1 | NULL | 4 | Lin Chaoying | 93 | F | | 23 | Ma Chao | 23 | M | 4 | NULL | 1 | Song Jiang | 45 | M | | 23 | Ma Chao | 23 | M | 4 | NULL | 2 | Zhang Sanfeng | 94 | M | | 23 | Ma Chao | 23 | M | 4 | NULL | 3 | Miejue Shitai | 77 | F | | 23 | Ma Chao | 23 | M | 4 | NULL | 4 | Lin Chaoying | 93 | F | | 24 | Xu Xian | 27 | M | NULL | NULL | 1 | Song Jiang | 45 | M | | 24 | Xu Xian | 27 | M | NULL | NULL | 2 | Zhang Sanfeng | 94 | M | | 24 | Xu Xian | 27 | M | NULL | NULL | 3 | Miejue Shitai | 77 | F | | 24 | Xu Xian | 27 | M | NULL | NULL | 4 | Lin Chaoying | 93 | F | | 25 | Sun Dasheng | 100 | M | NULL | NULL | 1 | Song Jiang | 45 | M | | 25 | Sun Dasheng | 100 | M | NULL | NULL | 2 | Zhang Sanfeng | 94 | M | | 25 | Sun Dasheng | 100 | M | NULL | NULL | 3 | Miejue Shitai | 77 | F | | 25 | Sun Dasheng | 100 | M | NULL | NULL | 4 | Lin Chaoying | 93 | F | +-------+---------------+-----+--------+---------+-----------+-----+---------------+-----+--------+ 100 rows in set (0.00 sec) MariaDB [yinzhengjie]>
3>.內鏈接查詢
等值鏈接：讓表之間的字段以「等值」創建鏈接關係；
不等值鏈接
天然鏈接:去掉重複列的等值鏈接
自鏈接
MariaDB [yinzhengjie]> SELECT * FROM students; +-------+---------------+-----+--------+---------+-----------+ | StuID | Name | Age | Gender | ClassID | TeacherID | +-------+---------------+-----+--------+---------+-----------+ | 1 | Shi Zhongyu | 22 | M | 2 | 3 | | 2 | Shi Potian | 22 | M | 1 | 7 | | 3 | Xie Yanke | 53 | M | 2 | 16 | | 4 | Ding Dian | 32 | M | 4 | 4 | | 5 | Yu Yutong | 26 | M | 3 | 1 | | 6 | Shi Qing | 46 | M | 5 | NULL | | 7 | Xi Ren | 19 | F | 3 | NULL | | 8 | Lin Daiyu | 17 | F | 7 | NULL | | 9 | Ren Yingying | 20 | F | 6 | NULL | | 10 | Yue Lingshan | 19 | F | 3 | NULL | | 11 | Yuan Chengzhi | 23 | M | 6 | NULL | | 12 | Wen Qingqing | 19 | F | 1 | NULL | | 13 | Tian Boguang | 33 | M | 2 | NULL | | 14 | Lu Wushuang | 17 | F | 3 | NULL | | 15 | Duan Yu | 19 | M | 4 | NULL | | 16 | Xu Zhu | 21 | M | 1 | NULL | | 17 | Lin Chong | 25 | M | 4 | NULL | | 18 | Hua Rong | 23 | M | 7 | NULL | | 19 | Xue Baochai | 18 | F | 6 | NULL | | 20 | Diao Chan | 19 | F | 7 | NULL | | 21 | Huang Yueying | 22 | F | 6 | NULL | | 22 | Xiao Qiao | 20 | F | 1 | NULL | | 23 | Ma Chao | 23 | M | 4 | NULL | | 24 | Xu Xian | 27 | M | NULL | NULL | | 25 | Sun Dasheng | 100 | M | NULL | NULL | +-------+---------------+-----+--------+---------+-----------+ 25 rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]> SELECT * FROM teachers; +-----+---------------+-----+--------+ | TID | Name | Age | Gender | +-----+---------------+-----+--------+ | 1 | Song Jiang | 45 | M | | 2 | Zhang Sanfeng | 94 | M | | 3 | Miejue Shitai | 77 | F | | 4 | Lin Chaoying | 93 | F | +-----+---------------+-----+--------+ 4 rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]> SELECT * FROM students,teachers WHERE students.TeacherID = teachers.TID; #該寫法太老，不推薦使用 +-------+-------------+-----+--------+---------+-----------+-----+---------------+-----+--------+ | StuID | Name | Age | Gender | ClassID | TeacherID | TID | Name | Age | Gender | +-------+-------------+-----+--------+---------+-----------+-----+---------------+-----+--------+ | 5 | Yu Yutong | 26 | M | 3 | 1 | 1 | Song Jiang | 45 | M | | 1 | Shi Zhongyu | 22 | M | 2 | 3 | 3 | Miejue Shitai | 77 | F | | 4 | Ding Dian | 32 | M | 4 | 4 | 4 | Lin Chaoying | 93 | F | +-------+-------------+-----+--------+---------+-----------+-----+---------------+-----+--------+ 3 rows in set (0.00 sec) MariaDB [yinzhengjie]>
MariaDB [yinzhengjie]> SELECT * FROM students; +-------+---------------+-----+--------+---------+-----------+ | StuID | Name | Age | Gender | ClassID | TeacherID | +-------+---------------+-----+--------+---------+-----------+ | 1 | Shi Zhongyu | 22 | M | 2 | 3 | | 2 | Shi Potian | 22 | M | 1 | 7 | | 3 | Xie Yanke | 53 | M | 2 | 16 | | 4 | Ding Dian | 32 | M | 4 | 4 | | 5 | Yu Yutong | 26 | M | 3 | 1 | | 6 | Shi Qing | 46 | M | 5 | NULL | | 7 | Xi Ren | 19 | F | 3 | NULL | | 8 | Lin Daiyu | 17 | F | 7 | NULL | | 9 | Ren Yingying | 20 | F | 6 | NULL | | 10 | Yue Lingshan | 19 | F | 3 | NULL | | 11 | Yuan Chengzhi | 23 | M | 6 | NULL | | 12 | Wen Qingqing | 19 | F | 1 | NULL | | 13 | Tian Boguang | 33 | M | 2 | NULL | | 14 | Lu Wushuang | 17 | F | 3 | NULL | | 15 | Duan Yu | 19 | M | 4 | NULL | | 16 | Xu Zhu | 21 | M | 1 | NULL | | 17 | Lin Chong | 25 | M | 4 | NULL | | 18 | Hua Rong | 23 | M | 7 | NULL | | 19 | Xue Baochai | 18 | F | 6 | NULL | | 20 | Diao Chan | 19 | F | 7 | NULL | | 21 | Huang Yueying | 22 | F | 6 | NULL | | 22 | Xiao Qiao | 20 | F | 1 | NULL | | 23 | Ma Chao | 23 | M | 4 | NULL | | 24 | Xu Xian | 27 | M | NULL | NULL | | 25 | Sun Dasheng | 100 | M | NULL | NULL | +-------+---------------+-----+--------+---------+-----------+ 25 rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]> SELECT * FROM teachers; +-----+---------------+-----+--------+ | TID | Name | Age | Gender | +-----+---------------+-----+--------+ | 1 | Song Jiang | 45 | M | | 2 | Zhang Sanfeng | 94 | M | | 3 | Miejue Shitai | 77 | F | | 4 | Lin Chaoying | 93 | F | +-----+---------------+-----+--------+ 4 rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]> SELECT * FROM students INNER JOIN teachers ON students.TeacherID = teachers.TID; #內鏈接查詢，推薦使用該寫法 +-------+-------------+-----+--------+---------+-----------+-----+---------------+-----+--------+ | StuID | Name | Age | Gender | ClassID | TeacherID | TID | Name | Age | Gender | +-------+-------------+-----+--------+---------+-----------+-----+---------------+-----+--------+ | 5 | Yu Yutong | 26 | M | 3 | 1 | 1 | Song Jiang | 45 | M | | 1 | Shi Zhongyu | 22 | M | 2 | 3 | 3 | Miejue Shitai | 77 | F | | 4 | Ding Dian | 32 | M | 4 | 4 | 4 | Lin Chaoying | 93 | F | +-------+-------------+-----+--------+---------+-----------+-----+---------------+-----+--------+ 3 rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]>
MariaDB [yinzhengjie]> SELECT * FROM students; +-------+---------------+-----+--------+---------+-----------+ | StuID | Name | Age | Gender | ClassID | TeacherID | +-------+---------------+-----+--------+---------+-----------+ | 1 | Shi Zhongyu | 22 | M | 2 | 3 | | 2 | Shi Potian | 22 | M | 1 | 7 | | 3 | Xie Yanke | 53 | M | 2 | 16 | | 4 | Ding Dian | 32 | M | 4 | 4 | | 5 | Yu Yutong | 26 | M | 3 | 1 | | 6 | Shi Qing | 46 | M | 5 | NULL | | 7 | Xi Ren | 19 | F | 3 | NULL | | 8 | Lin Daiyu | 17 | F | 7 | NULL | | 9 | Ren Yingying | 20 | F | 6 | NULL | | 10 | Yue Lingshan | 19 | F | 3 | NULL | | 11 | Yuan Chengzhi | 23 | M | 6 | NULL | | 12 | Wen Qingqing | 19 | F | 1 | NULL | | 13 | Tian Boguang | 33 | M | 2 | NULL | | 14 | Lu Wushuang | 17 | F | 3 | NULL | | 15 | Duan Yu | 19 | M | 4 | NULL | | 16 | Xu Zhu | 21 | M | 1 | NULL | | 17 | Lin Chong | 25 | M | 4 | NULL | | 18 | Hua Rong | 23 | M | 7 | NULL | | 19 | Xue Baochai | 18 | F | 6 | NULL | | 20 | Diao Chan | 19 | F | 7 | NULL | | 21 | Huang Yueying | 22 | F | 6 | NULL | | 22 | Xiao Qiao | 20 | F | 1 | NULL | | 23 | Ma Chao | 23 | M | 4 | NULL | | 24 | Xu Xian | 27 | M | NULL | NULL | | 25 | Sun Dasheng | 100 | M | NULL | NULL | +-------+---------------+-----+--------+---------+-----------+ 25 rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]> SELECT * FROM teachers; +-----+---------------+-----+--------+ | TID | Name | Age | Gender | +-----+---------------+-----+--------+ | 1 | Song Jiang | 45 | M | | 2 | Zhang Sanfeng | 94 | M | | 3 | Miejue Shitai | 77 | F | | 4 | Lin Chaoying | 93 | F | +-----+---------------+-----+--------+ 4 rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]> SELECT stuid,s.name AS 學生姓名 ,tid,t.name AS 老師姓名 FROM students AS s INNER JOIN teachers AS t ON s.TeacherID = t.TID; #查詢制定者字段並設置字段別名,也爲表名設置別名進行調用。 +-------+--------------+-----+---------------+ | stuid | 學生姓名 | tid | 老師姓名 | +-------+--------------+-----+---------------+ | 5 | Yu Yutong | 1 | Song Jiang | | 1 | Shi Zhongyu | 3 | Miejue Shitai | | 4 | Ding Dian | 4 | Lin Chaoying | +-------+--------------+-----+---------------+ 3 rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]>
MariaDB [yinzhengjie]> CREATE TABLE emp(id int,name char(3),leaderid int); Query OK, 0 rows affected (0.01 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]> DESC emp; +----------+---------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +----------+---------+------+-----+---------+-------+ | id | int(11) | YES | | NULL | | | name | char(3) | YES | | NULL | | | leaderid | int(11) | YES | | NULL | | +----------+---------+------+-----+---------+-------+ rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]> INSERT INTO emp VALUES(1,'張無忌',null),(2,'楊逍',1),(3,'範遙',2),(4,'殷天正',2),(5,'韋一笑',2); Query OK, 5 rows affected (0.00 sec) Records: 5 Duplicates: 0 Warnings: 0 MariaDB [yinzhengjie]> MariaDB [yinzhengjie]> SELECT * FROM emp; +------+-----------+----------+ | id | name | leaderid | +------+-----------+----------+ | 1 | 張無忌 | NULL | | 2 | 楊逍 | 1 | | 3 | 範遙 | 2 | | 4 | 殷天正 | 2 | | 5 | 韋一笑 | 2 | +------+-----------+----------+ rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]> SELECT a.name,b.name AS 領導 FROM emp AS a LEFT OUTER JOIN emp AS b ON a.leaderid = b.id; #同一張表查詢數據，查詢每一個人及其領導的姓名。(自鏈接查詢) +-----------+-----------+ | name | 領導 | +-----------+-----------+ | 楊逍 | 張無忌 | | 範遙 | 楊逍 | | 殷天正 | 楊逍 | | 韋一笑 | 楊逍 | | 張無忌 | NULL | +-----------+-----------+ rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]>
4>.子查詢
子查詢：在查詢語句嵌套着查詢語句，性能較差
基於某語句的查詢結果再次進行的查詢
用在WHERE子句中的子查詢
用於比較表達式中的子查詢；子查詢僅能返回單個值
SELECT Name,Age FROM students WHERE Age>(SELECT avg(Age) FROM students);
用於IN中的子查詢：子查詢應該單鍵查詢並返回一個或多個值從構成列表
SELECT Name,Age FROM students WHERE Age IN (SELECT Age FROM teachers);
用於EXISTS
用於FROM子句中的子查詢
使用格式：SELECT tb_alias.col1,... FROM (SELECT clause) AS tb_alias WHERE Clause;
示例：
SELECT s.aage,s.ClassID FROM (SELECT avg(Age) AS aage,ClassID FROM students WHERE ClassID IS NOT NULL GROUP BY ClassID) AS s WHERE s.aage>30;
MariaDB [yinzhengjie]> SELECT AVG(age) FROM students; +----------+ | AVG(age) | +----------+ | 27.4000 | +----------+ row in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]> SELECT * FROM teachers; +-----+---------------+-----+--------+ | TID | Name | Age | Gender | +-----+---------------+-----+--------+ | 1 | Song Jiang | 45 | M | | 2 | Zhang Sanfeng | 94 | M | | 3 | Miejue Shitai | 77 | F | | 4 | Lin Chaoying | 93 | F | +-----+---------------+-----+--------+ rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]> SELECT * FROM teachers WHERE age > (SELECT AVG(age) FROM students) * 2; +-----+---------------+-----+--------+ | TID | Name | Age | Gender | +-----+---------------+-----+--------+ | 2 | Zhang Sanfeng | 94 | M | | 3 | Miejue Shitai | 77 | F | | 4 | Lin Chaoying | 93 | F | +-----+---------------+-----+--------+ rows in set (0.00 sec) MariaDB [yinzhengjie]>
5>.外鏈接查詢
左外鏈接： FROM tb1 LEFT JOIN tb2 ON tb1.col=tb2.col
右外鏈接 FROM tb1 RIGHT JOIN tb2 ON tb1.col=tb2.col
MariaDB [yinzhengjie]> SELECT * FROM teachers; +-----+---------------+-----+--------+ | TID | Name | Age | Gender | +-----+---------------+-----+--------+ | 1 | Song Jiang | 45 | M | | 2 | Zhang Sanfeng | 94 | M | | 3 | Miejue Shitai | 77 | F | | 4 | Lin Chaoying | 93 | F | +-----+---------------+-----+--------+ 4 rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]> SELECT * FROM students; +-------+---------------+-----+--------+---------+-----------+ | StuID | Name | Age | Gender | ClassID | TeacherID | +-------+---------------+-----+--------+---------+-----------+ | 1 | Shi Zhongyu | 22 | M | 2 | 3 | | 2 | Shi Potian | 22 | M | 1 | 7 | | 3 | Xie Yanke | 53 | M | 2 | 16 | | 4 | Ding Dian | 32 | M | 4 | 4 | | 5 | Yu Yutong | 26 | M | 3 | 1 | | 6 | Shi Qing | 46 | M | 5 | NULL | | 7 | Xi Ren | 19 | F | 3 | NULL | | 8 | Lin Daiyu | 17 | F | 7 | NULL | | 9 | Ren Yingying | 20 | F | 6 | NULL | | 10 | Yue Lingshan | 19 | F | 3 | NULL | | 11 | Yuan Chengzhi | 23 | M | 6 | NULL | | 12 | Wen Qingqing | 19 | F | 1 | NULL | | 13 | Tian Boguang | 33 | M | 2 | NULL | | 14 | Lu Wushuang | 17 | F | 3 | NULL | | 15 | Duan Yu | 19 | M | 4 | NULL | | 16 | Xu Zhu | 21 | M | 1 | NULL | | 17 | Lin Chong | 25 | M | 4 | NULL | | 18 | Hua Rong | 23 | M | 7 | NULL | | 19 | Xue Baochai | 18 | F | 6 | NULL | | 20 | Diao Chan | 19 | F | 7 | NULL | | 21 | Huang Yueying | 22 | F | 6 | NULL | | 22 | Xiao Qiao | 20 | F | 1 | NULL | | 23 | Ma Chao | 23 | M | 4 | NULL | | 24 | Xu Xian | 27 | M | NULL | NULL | | 25 | Sun Dasheng | 100 | M | NULL | NULL | +-------+---------------+-----+--------+---------+-----------+ 25 rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]> SELECT * FROM students AS s LEFT OUTER JOIN teachers AS t ON s.TeacherID = t.TID; #左外鏈接，以students表(在左邊)記錄爲校驗 +-------+---------------+-----+--------+---------+-----------+------+---------------+------+--------+ | StuID | Name | Age | Gender | ClassID | TeacherID | TID | Name | Age | Gender | +-------+---------------+-----+--------+---------+-----------+------+---------------+------+--------+ | 1 | Shi Zhongyu | 22 | M | 2 | 3 | 3 | Miejue Shitai | 77 | F | | 2 | Shi Potian | 22 | M | 1 | 7 | NULL | NULL | NULL | NULL | | 3 | Xie Yanke | 53 | M | 2 | 16 | NULL | NULL | NULL | NULL | | 4 | Ding Dian | 32 | M | 4 | 4 | 4 | Lin Chaoying | 93 | F | | 5 | Yu Yutong | 26 | M | 3 | 1 | 1 | Song Jiang | 45 | M | | 6 | Shi Qing | 46 | M | 5 | NULL | NULL | NULL | NULL | NULL | | 7 | Xi Ren | 19 | F | 3 | NULL | NULL | NULL | NULL | NULL | | 8 | Lin Daiyu | 17 | F | 7 | NULL | NULL | NULL | NULL | NULL | | 9 | Ren Yingying | 20 | F | 6 | NULL | NULL | NULL | NULL | NULL | | 10 | Yue Lingshan | 19 | F | 3 | NULL | NULL | NULL | NULL | NULL | | 11 | Yuan Chengzhi | 23 | M | 6 | NULL | NULL | NULL | NULL | NULL | | 12 | Wen Qingqing | 19 | F | 1 | NULL | NULL | NULL | NULL | NULL | | 13 | Tian Boguang | 33 | M | 2 | NULL | NULL | NULL | NULL | NULL | | 14 | Lu Wushuang | 17 | F | 3 | NULL | NULL | NULL | NULL | NULL | | 15 | Duan Yu | 19 | M | 4 | NULL | NULL | NULL | NULL | NULL | | 16 | Xu Zhu | 21 | M | 1 | NULL | NULL | NULL | NULL | NULL | | 17 | Lin Chong | 25 | M | 4 | NULL | NULL | NULL | NULL | NULL | | 18 | Hua Rong | 23 | M | 7 | NULL | NULL | NULL | NULL | NULL | | 19 | Xue Baochai | 18 | F | 6 | NULL | NULL | NULL | NULL | NULL | | 20 | Diao Chan | 19 | F | 7 | NULL | NULL | NULL | NULL | NULL | | 21 | Huang Yueying | 22 | F | 6 | NULL | NULL | NULL | NULL | NULL | | 22 | Xiao Qiao | 20 | F | 1 | NULL | NULL | NULL | NULL | NULL | | 23 | Ma Chao | 23 | M | 4 | NULL | NULL | NULL | NULL | NULL | | 24 | Xu Xian | 27 | M | NULL | NULL | NULL | NULL | NULL | NULL | | 25 | Sun Dasheng | 100 | M | NULL | NULL | NULL | NULL | NULL | NULL | +-------+---------------+-----+--------+---------+-----------+------+---------------+------+--------+ 25 rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]>
MariaDB [yinzhengjie]> SELECT * FROM teachers; +-----+---------------+-----+--------+ | TID | Name | Age | Gender | +-----+---------------+-----+--------+ | 1 | Song Jiang | 45 | M | | 2 | Zhang Sanfeng | 94 | M | | 3 | Miejue Shitai | 77 | F | | 4 | Lin Chaoying | 93 | F | +-----+---------------+-----+--------+ 4 rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]> SELECT * FROM students; +-------+---------------+-----+--------+---------+-----------+ | StuID | Name | Age | Gender | ClassID | TeacherID | +-------+---------------+-----+--------+---------+-----------+ | 1 | Shi Zhongyu | 22 | M | 2 | 3 | | 2 | Shi Potian | 22 | M | 1 | 7 | | 3 | Xie Yanke | 53 | M | 2 | 16 | | 4 | Ding Dian | 32 | M | 4 | 4 | | 5 | Yu Yutong | 26 | M | 3 | 1 | | 6 | Shi Qing | 46 | M | 5 | NULL | | 7 | Xi Ren | 19 | F | 3 | NULL | | 8 | Lin Daiyu | 17 | F | 7 | NULL | | 9 | Ren Yingying | 20 | F | 6 | NULL | | 10 | Yue Lingshan | 19 | F | 3 | NULL | | 11 | Yuan Chengzhi | 23 | M | 6 | NULL | | 12 | Wen Qingqing | 19 | F | 1 | NULL | | 13 | Tian Boguang | 33 | M | 2 | NULL | | 14 | Lu Wushuang | 17 | F | 3 | NULL | | 15 | Duan Yu | 19 | M | 4 | NULL | | 16 | Xu Zhu | 21 | M | 1 | NULL | | 17 | Lin Chong | 25 | M | 4 | NULL | | 18 | Hua Rong | 23 | M | 7 | NULL | | 19 | Xue Baochai | 18 | F | 6 | NULL | | 20 | Diao Chan | 19 | F | 7 | NULL | | 21 | Huang Yueying | 22 | F | 6 | NULL | | 22 | Xiao Qiao | 20 | F | 1 | NULL | | 23 | Ma Chao | 23 | M | 4 | NULL | | 24 | Xu Xian | 27 | M | NULL | NULL | | 25 | Sun Dasheng | 100 | M | NULL | NULL | +-------+---------------+-----+--------+---------+-----------+ 25 rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]> SELECT * FROM students AS s RIGHT OUTER JOIN teachers AS t ON s.TeacherID = t.TID; #右外鏈接,以"teachers"(在右邊)表記錄爲校驗 +-------+-------------+------+--------+---------+-----------+-----+---------------+-----+--------+ | StuID | Name | Age | Gender | ClassID | TeacherID | TID | Name | Age | Gender | +-------+-------------+------+--------+---------+-----------+-----+---------------+-----+--------+ | 1 | Shi Zhongyu | 22 | M | 2 | 3 | 3 | Miejue Shitai | 77 | F | | 4 | Ding Dian | 32 | M | 4 | 4 | 4 | Lin Chaoying | 93 | F | | 5 | Yu Yutong | 26 | M | 3 | 1 | 1 | Song Jiang | 45 | M | | NULL | NULL | NULL | NULL | NULL | NULL | 2 | Zhang Sanfeng | 94 | M | +-------+-------------+------+--------+---------+-----------+-----+---------------+-----+--------+ 4 rows in set (0.00 sec) MariaDB [yinzhengjie]>
MariaDB [yinzhengjie]> SELECT * FROM students AS s LEFT OUTER JOIN teachers AS t ON s.TeacherID = t.TID; +-------+---------------+-----+--------+---------+-----------+------+---------------+------+--------+ | StuID | Name | Age | Gender | ClassID | TeacherID | TID | Name | Age | Gender | +-------+---------------+-----+--------+---------+-----------+------+---------------+------+--------+ | 1 | Shi Zhongyu | 22 | M | 2 | 3 | 3 | Miejue Shitai | 77 | F | | 2 | Shi Potian | 22 | M | 1 | 7 | NULL | NULL | NULL | NULL | | 3 | Xie Yanke | 53 | M | 2 | 16 | NULL | NULL | NULL | NULL | | 4 | Ding Dian | 32 | M | 4 | 4 | 4 | Lin Chaoying | 93 | F | | 5 | Yu Yutong | 26 | M | 3 | 1 | 1 | Song Jiang | 45 | M | | 6 | Shi Qing | 46 | M | 5 | NULL | NULL | NULL | NULL | NULL | | 7 | Xi Ren | 19 | F | 3 | NULL | NULL | NULL | NULL | NULL | | 8 | Lin Daiyu | 17 | F | 7 | NULL | NULL | NULL | NULL | NULL | | 9 | Ren Yingying | 20 | F | 6 | NULL | NULL | NULL | NULL | NULL | | 10 | Yue Lingshan | 19 | F | 3 | NULL | NULL | NULL | NULL | NULL | | 11 | Yuan Chengzhi | 23 | M | 6 | NULL | NULL | NULL | NULL | NULL | | 12 | Wen Qingqing | 19 | F | 1 | NULL | NULL | NULL | NULL | NULL | | 13 | Tian Boguang | 33 | M | 2 | NULL | NULL | NULL | NULL | NULL | | 14 | Lu Wushuang | 17 | F | 3 | NULL | NULL | NULL | NULL | NULL | | 15 | Duan Yu | 19 | M | 4 | NULL | NULL | NULL | NULL | NULL | | 16 | Xu Zhu | 21 | M | 1 | NULL | NULL | NULL | NULL | NULL | | 17 | Lin Chong | 25 | M | 4 | NULL | NULL | NULL | NULL | NULL | | 18 | Hua Rong | 23 | M | 7 | NULL | NULL | NULL | NULL | NULL | | 19 | Xue Baochai | 18 | F | 6 | NULL | NULL | NULL | NULL | NULL | | 20 | Diao Chan | 19 | F | 7 | NULL | NULL | NULL | NULL | NULL | | 21 | Huang Yueying | 22 | F | 6 | NULL | NULL | NULL | NULL | NULL | | 22 | Xiao Qiao | 20 | F | 1 | NULL | NULL | NULL | NULL | NULL | | 23 | Ma Chao | 23 | M | 4 | NULL | NULL | NULL | NULL | NULL | | 24 | Xu Xian | 27 | M | NULL | NULL | NULL | NULL | NULL | NULL | | 25 | Sun Dasheng | 100 | M | NULL | NULL | NULL | NULL | NULL | NULL | +-------+---------------+-----+--------+---------+-----------+------+---------------+------+--------+ 25 rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]> SELECT * FROM students AS s LEFT OUTER JOIN teachers AS t ON s.TeacherID = t.TID WHERE t.tid IS NULL; #對左外鏈接再次進行過濾，將兩個表中重複的數據剔除。 +-------+---------------+-----+--------+---------+-----------+------+------+------+--------+ | StuID | Name | Age | Gender | ClassID | TeacherID | TID | Name | Age | Gender | +-------+---------------+-----+--------+---------+-----------+------+------+------+--------+ | 2 | Shi Potian | 22 | M | 1 | 7 | NULL | NULL | NULL | NULL | | 3 | Xie Yanke | 53 | M | 2 | 16 | NULL | NULL | NULL | NULL | | 6 | Shi Qing | 46 | M | 5 | NULL | NULL | NULL | NULL | NULL | | 7 | Xi Ren | 19 | F | 3 | NULL | NULL | NULL | NULL | NULL | | 8 | Lin Daiyu | 17 | F | 7 | NULL | NULL | NULL | NULL | NULL | | 9 | Ren Yingying | 20 | F | 6 | NULL | NULL | NULL | NULL | NULL | | 10 | Yue Lingshan | 19 | F | 3 | NULL | NULL | NULL | NULL | NULL | | 11 | Yuan Chengzhi | 23 | M | 6 | NULL | NULL | NULL | NULL | NULL | | 12 | Wen Qingqing | 19 | F | 1 | NULL | NULL | NULL | NULL | NULL | | 13 | Tian Boguang | 33 | M | 2 | NULL | NULL | NULL | NULL | NULL | | 14 | Lu Wushuang | 17 | F | 3 | NULL | NULL | NULL | NULL | NULL | | 15 | Duan Yu | 19 | M | 4 | NULL | NULL | NULL | NULL | NULL | | 16 | Xu Zhu | 21 | M | 1 | NULL | NULL | NULL | NULL | NULL | | 17 | Lin Chong | 25 | M | 4 | NULL | NULL | NULL | NULL | NULL | | 18 | Hua Rong | 23 | M | 7 | NULL | NULL | NULL | NULL | NULL | | 19 | Xue Baochai | 18 | F | 6 | NULL | NULL | NULL | NULL | NULL | | 20 | Diao Chan | 19 | F | 7 | NULL | NULL | NULL | NULL | NULL | | 21 | Huang Yueying | 22 | F | 6 | NULL | NULL | NULL | NULL | NULL | | 22 | Xiao Qiao | 20 | F | 1 | NULL | NULL | NULL | NULL | NULL | | 23 | Ma Chao | 23 | M | 4 | NULL | NULL | NULL | NULL | NULL | | 24 | Xu Xian | 27 | M | NULL | NULL | NULL | NULL | NULL | NULL | | 25 | Sun Dasheng | 100 | M | NULL | NULL | NULL | NULL | NULL | NULL | +-------+---------------+-----+--------+---------+-----------+------+------+------+--------+ 22 rows in set (0.00 sec) MariaDB [yinzhengjie]>
MariaDB [yinzhengjie]> SELECT * FROM teachers; +-----+---------------+-----+--------+ | TID | Name | Age | Gender | +-----+---------------+-----+--------+ | 1 | Song Jiang | 45 | M | | 2 | Zhang Sanfeng | 94 | M | | 3 | Miejue Shitai | 77 | F | | 4 | Lin Chaoying | 93 | F | +-----+---------------+-----+--------+ 4 rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]> SELECT * FROM students; +-------+---------------+-----+--------+---------+-----------+ | StuID | Name | Age | Gender | ClassID | TeacherID | +-------+---------------+-----+--------+---------+-----------+ | 1 | Shi Zhongyu | 22 | M | 2 | 3 | | 2 | Shi Potian | 22 | M | 1 | 7 | | 3 | Xie Yanke | 53 | M | 2 | 16 | | 4 | Ding Dian | 32 | M | 4 | 4 | | 5 | Yu Yutong | 26 | M | 3 | 1 | | 6 | Shi Qing | 46 | M | 5 | NULL | | 7 | Xi Ren | 19 | F | 3 | NULL | | 8 | Lin Daiyu | 17 | F | 7 | NULL | | 9 | Ren Yingying | 20 | F | 6 | NULL | | 10 | Yue Lingshan | 19 | F | 3 | NULL | | 11 | Yuan Chengzhi | 23 | M | 6 | NULL | | 12 | Wen Qingqing | 19 | F | 1 | NULL | | 13 | Tian Boguang | 33 | M | 2 | NULL | | 14 | Lu Wushuang | 17 | F | 3 | NULL | | 15 | Duan Yu | 19 | M | 4 | NULL | | 16 | Xu Zhu | 21 | M | 1 | NULL | | 17 | Lin Chong | 25 | M | 4 | NULL | | 18 | Hua Rong | 23 | M | 7 | NULL | | 19 | Xue Baochai | 18 | F | 6 | NULL | | 20 | Diao Chan | 19 | F | 7 | NULL | | 21 | Huang Yueying | 22 | F | 6 | NULL | | 22 | Xiao Qiao | 20 | F | 1 | NULL | | 23 | Ma Chao | 23 | M | 4 | NULL | | 24 | Xu Xian | 27 | M | NULL | NULL | | 25 | Sun Dasheng | 100 | M | NULL | NULL | +-------+---------------+-----+--------+---------+-----------+ 25 rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]> SELECT * FROM students AS s RIGHT OUTER JOIN teachers AS t ON s.TeacherID = t.TID; +-------+-------------+------+--------+---------+-----------+-----+---------------+-----+--------+ | StuID | Name | Age | Gender | ClassID | TeacherID | TID | Name | Age | Gender | +-------+-------------+------+--------+---------+-----------+-----+---------------+-----+--------+ | 1 | Shi Zhongyu | 22 | M | 2 | 3 | 3 | Miejue Shitai | 77 | F | | 4 | Ding Dian | 32 | M | 4 | 4 | 4 | Lin Chaoying | 93 | F | | 5 | Yu Yutong | 26 | M | 3 | 1 | 1 | Song Jiang | 45 | M | | NULL | NULL | NULL | NULL | NULL | NULL | 2 | Zhang Sanfeng | 94 | M | +-------+-------------+------+--------+---------+-----------+-----+---------------+-----+--------+ 4 rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]> SELECT * FROM students AS s RIGHT OUTER JOIN teachers AS t ON s.TeacherID = t.TID WHERE s.teacherid IS NULL; #對右外鏈接再次進行過濾，將重複的數據剔除掉。 +-------+------+------+--------+---------+-----------+-----+---------------+-----+--------+ | StuID | Name | Age | Gender | ClassID | TeacherID | TID | Name | Age | Gender | +-------+------+------+--------+---------+-----------+-----+---------------+-----+--------+ | NULL | NULL | NULL | NULL | NULL | NULL | 2 | Zhang Sanfeng | 94 | M | +-------+------+------+--------+---------+-----------+-----+---------------+-----+--------+ 1 row in set (0.00 sec) MariaDB [yinzhengjie]>
MariaDB [yinzhengjie]> SELECT * FROM teachers; +-----+---------------+-----+--------+ | TID | Name | Age | Gender | +-----+---------------+-----+--------+ | 1 | Song Jiang | 45 | M | | 2 | Zhang Sanfeng | 94 | M | | 3 | Miejue Shitai | 77 | F | | 4 | Lin Chaoying | 93 | F | +-----+---------------+-----+--------+ 4 rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]> SELECT * FROM students; +-------+---------------+-----+--------+---------+-----------+ | StuID | Name | Age | Gender | ClassID | TeacherID | +-------+---------------+-----+--------+---------+-----------+ | 1 | Shi Zhongyu | 22 | M | 2 | 3 | | 2 | Shi Potian | 22 | M | 1 | 7 | | 3 | Xie Yanke | 53 | M | 2 | 16 | | 4 | Ding Dian | 32 | M | 4 | 4 | | 5 | Yu Yutong | 26 | M | 3 | 1 | | 6 | Shi Qing | 46 | M | 5 | NULL | | 7 | Xi Ren | 19 | F | 3 | NULL | | 8 | Lin Daiyu | 17 | F | 7 | NULL | | 9 | Ren Yingying | 20 | F | 6 | NULL | | 10 | Yue Lingshan | 19 | F | 3 | NULL | | 11 | Yuan Chengzhi | 23 | M | 6 | NULL | | 12 | Wen Qingqing | 19 | F | 1 | NULL | | 13 | Tian Boguang | 33 | M | 2 | NULL | | 14 | Lu Wushuang | 17 | F | 3 | NULL | | 15 | Duan Yu | 19 | M | 4 | NULL | | 16 | Xu Zhu | 21 | M | 1 | NULL | | 17 | Lin Chong | 25 | M | 4 | NULL | | 18 | Hua Rong | 23 | M | 7 | NULL | | 19 | Xue Baochai | 18 | F | 6 | NULL | | 20 | Diao Chan | 19 | F | 7 | NULL | | 21 | Huang Yueying | 22 | F | 6 | NULL | | 22 | Xiao Qiao | 20 | F | 1 | NULL | | 23 | Ma Chao | 23 | M | 4 | NULL | | 24 | Xu Xian | 27 | M | NULL | NULL | | 25 | Sun Dasheng | 100 | M | NULL | NULL | +-------+---------------+-----+--------+---------+-----------+ 25 rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]> SELECT * FROM students AS s FULL OUTER JOIN teachers AS t ON s.teacherid = t.tid; #MySQL/MariaDB不支持徹底外鏈接查詢 ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax t o use near 'FULL OUTER JOIN teachers AS t ON s.teacherid = t.tid' at line 1 MariaDB [yinzhengjie]> MariaDB [yinzhengjie]> SELECT * FROM students AS s LEFT OUTER JOIN teachers AS t ON s.TeacherID = t.TID UNION SELECT * FROM students AS s RIGHT O UTER JOIN teachers AS t ON s.TeacherID = t.TID; #因爲MySQL/MariaDB不支持徹底外鏈接查詢，可是咱們可使用左外鏈接與右外鏈接的查詢結果經過UNION去重功能實現徹底外鏈接查詢功能。 +-------+---------------+------+--------+---------+-----------+------+---------------+------+--------+ | StuID | Name | Age | Gender | ClassID | TeacherID | TID | Name | Age | Gender | +-------+---------------+------+--------+---------+-----------+------+---------------+------+--------+ | 1 | Shi Zhongyu | 22 | M | 2 | 3 | 3 | Miejue Shitai | 77 | F | | 2 | Shi Potian | 22 | M | 1 | 7 | NULL | NULL | NULL | NULL | | 3 | Xie Yanke | 53 | M | 2 | 16 | NULL | NULL | NULL | NULL | | 4 | Ding Dian | 32 | M | 4 | 4 | 4 | Lin Chaoying | 93 | F | | 5 | Yu Yutong | 26 | M | 3 | 1 | 1 | Song Jiang | 45 | M | | 6 | Shi Qing | 46 | M | 5 | NULL | NULL | NULL | NULL | NULL | | 7 | Xi Ren | 19 | F | 3 | NULL | NULL | NULL | NULL | NULL | | 8 | Lin Daiyu | 17 | F | 7 | NULL | NULL | NULL | NULL | NULL | | 9 | Ren Yingying | 20 | F | 6 | NULL | NULL | NULL | NULL | NULL | | 10 | Yue Lingshan | 19 | F | 3 | NULL | NULL | NULL | NULL | NULL | | 11 | Yuan Chengzhi | 23 | M | 6 | NULL | NULL | NULL | NULL | NULL | | 12 | Wen Qingqing | 19 | F | 1 | NULL | NULL | NULL | NULL | NULL | | 13 | Tian Boguang | 33 | M | 2 | NULL | NULL | NULL | NULL | NULL | | 14 | Lu Wushuang | 17 | F | 3 | NULL | NULL | NULL | NULL | NULL | | 15 | Duan Yu | 19 | M | 4 | NULL | NULL | NULL | NULL | NULL | | 16 | Xu Zhu | 21 | M | 1 | NULL | NULL | NULL | NULL | NULL | | 17 | Lin Chong | 25 | M | 4 | NULL | NULL | NULL | NULL | NULL | | 18 | Hua Rong | 23 | M | 7 | NULL | NULL | NULL | NULL | NULL | | 19 | Xue Baochai | 18 | F | 6 | NULL | NULL | NULL | NULL | NULL | | 20 | Diao Chan | 19 | F | 7 | NULL | NULL | NULL | NULL | NULL | | 21 | Huang Yueying | 22 | F | 6 | NULL | NULL | NULL | NULL | NULL | | 22 | Xiao Qiao | 20 | F | 1 | NULL | NULL | NULL | NULL | NULL | | 23 | Ma Chao | 23 | M | 4 | NULL | NULL | NULL | NULL | NULL | | 24 | Xu Xian | 27 | M | NULL | NULL | NULL | NULL | NULL | NULL | | 25 | Sun Dasheng | 100 | M | NULL | NULL | NULL | NULL | NULL | NULL | | NULL | NULL | NULL | NULL | NULL | NULL | 2 | Zhang Sanfeng | 94 | M | +-------+---------------+------+--------+---------+-----------+------+---------------+------+--------+ 26 rows in set (0.00 sec) MariaDB [yinzhengjie]>
MariaDB [yinzhengjie]> SELECT * FROM students; +-------+---------------+-----+--------+---------+-----------+ | StuID | Name | Age | Gender | ClassID | TeacherID | +-------+---------------+-----+--------+---------+-----------+ | 1 | Shi Zhongyu | 22 | M | 2 | 3 | | 2 | Shi Potian | 22 | M | 1 | 7 | | 3 | Xie Yanke | 53 | M | 2 | 16 | | 4 | Ding Dian | 32 | M | 4 | 4 | | 5 | Yu Yutong | 26 | M | 3 | 1 | | 6 | Shi Qing | 46 | M | 5 | NULL | | 7 | Xi Ren | 19 | F | 3 | NULL | | 8 | Lin Daiyu | 17 | F | 7 | NULL | | 9 | Ren Yingying | 20 | F | 6 | NULL | | 10 | Yue Lingshan | 19 | F | 3 | NULL | | 11 | Yuan Chengzhi | 23 | M | 6 | NULL | | 12 | Wen Qingqing | 19 | F | 1 | NULL | | 13 | Tian Boguang | 33 | M | 2 | NULL | | 14 | Lu Wushuang | 17 | F | 3 | NULL | | 15 | Duan Yu | 19 | M | 4 | NULL | | 16 | Xu Zhu | 21 | M | 1 | NULL | | 17 | Lin Chong | 25 | M | 4 | NULL | | 18 | Hua Rong | 23 | M | 7 | NULL | | 19 | Xue Baochai | 18 | F | 6 | NULL | | 20 | Diao Chan | 19 | F | 7 | NULL | | 21 | Huang Yueying | 22 | F | 6 | NULL | | 22 | Xiao Qiao | 20 | F | 1 | NULL | | 23 | Ma Chao | 23 | M | 4 | NULL | | 24 | Xu Xian | 27 | M | NULL | NULL | | 25 | Sun Dasheng | 100 | M | NULL | NULL | +-------+---------------+-----+--------+---------+-----------+ 25 rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]> SELECT * FROM teachers; +-----+---------------+-----+--------+ | TID | Name | Age | Gender | +-----+---------------+-----+--------+ | 1 | Song Jiang | 45 | M | | 2 | Zhang Sanfeng | 94 | M | | 3 | Miejue Shitai | 77 | F | | 4 | Lin Chaoying | 93 | F | +-----+---------------+-----+--------+ 4 rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]> SELECT * FROM (SELECT stuid,s.name AS student_name,s.age AS student_age,s.gender AS student_gender,classid,teacherid,tid,t.name AS teacher_name,t.age AS teacher_age,t.gender AS teacher_gender FROM students AS s LEFT OUTER JOIN teachers AS t ON s.TeacherID = t.TID UNION SELECT stuid,s.name AS student_name,s.age AS student_age,s.gender AS student_gender,classid,teacherid,tid,t.name AS teacher_name,t.age AS teacher_age,t.gender AS teacher_gender FROM students AS s RIGHT OUTER JOIN teachers AS t ON s.TeacherID = t.TID) AS f WHERE f.teacherid IS NULL OR f.tid IS NULL; #將間接實現徹底外鏈接查詢結果再次進行過濾,查詢出徹底外鏈接中過濾掉兩表重複的數據。 +-------+---------------+-------------+----------------+---------+-----------+------+---------------+-------------+----------------+ | stuid | student_name | student_age | student_gender | classid | teacherid | tid | teacher_name | teacher_age | teacher_gender | +-------+---------------+-------------+----------------+---------+-----------+------+---------------+-------------+----------------+ | 2 | Shi Potian | 22 | M | 1 | 7 | NULL | NULL | NULL | NULL | | 3 | Xie Yanke | 53 | M | 2 | 16 | NULL | NULL | NULL | NULL | | 6 | Shi Qing | 46 | M | 5 | NULL | NULL | NULL | NULL | NULL | | 7 | Xi Ren | 19 | F | 3 | NULL | NULL | NULL | NULL | NULL | | 8 | Lin Daiyu | 17 | F | 7 | NULL | NULL | NULL | NULL | NULL | | 9 | Ren Yingying | 20 | F | 6 | NULL | NULL | NULL | NULL | NULL | | 10 | Yue Lingshan | 19 | F | 3 | NULL | NULL | NULL | NULL | NULL | | 11 | Yuan Chengzhi | 23 | M | 6 | NULL | NULL | NULL | NULL | NULL | | 12 | Wen Qingqing | 19 | F | 1 | NULL | NULL | NULL | NULL | NULL | | 13 | Tian Boguang | 33 | M | 2 | NULL | NULL | NULL | NULL | NULL | | 14 | Lu Wushuang | 17 | F | 3 | NULL | NULL | NULL | NULL | NULL | | 15 | Duan Yu | 19 | M | 4 | NULL | NULL | NULL | NULL | NULL | | 16 | Xu Zhu | 21 | M | 1 | NULL | NULL | NULL | NULL | NULL | | 17 | Lin Chong | 25 | M | 4 | NULL | NULL | NULL | NULL | NULL | | 18 | Hua Rong | 23 | M | 7 | NULL | NULL | NULL | NULL | NULL | | 19 | Xue Baochai | 18 | F | 6 | NULL | NULL | NULL | NULL | NULL | | 20 | Diao Chan | 19 | F | 7 | NULL | NULL | NULL | NULL | NULL | | 21 | Huang Yueying | 22 | F | 6 | NULL | NULL | NULL | NULL | NULL | | 22 | Xiao Qiao | 20 | F | 1 | NULL | NULL | NULL | NULL | NULL | | 23 | Ma Chao | 23 | M | 4 | NULL | NULL | NULL | NULL | NULL | | 24 | Xu Xian | 27 | M | NULL | NULL | NULL | NULL | NULL | NULL | | 25 | Sun Dasheng | 100 | M | NULL | NULL | NULL | NULL | NULL | NULL | | NULL | NULL | NULL | NULL | NULL | NULL | 2 | Zhang Sanfeng | 94 | M | +-------+---------------+-------------+----------------+---------+-----------+------+---------------+-------------+----------------+ 23 rows in set (0.00 sec) MariaDB [yinzhengjie]>
6>.自鏈接查詢
MariaDB [yinzhengjie]> CREATE TABLE emp(id int,name char(3),leaderid int); Query OK, 0 rows affected (0.01 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]> DESC emp; +----------+---------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +----------+---------+------+-----+---------+-------+ | id | int(11) | YES | | NULL | | | name | char(3) | YES | | NULL | | | leaderid | int(11) | YES | | NULL | | +----------+---------+------+-----+---------+-------+ rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]> INSERT INTO emp VALUES(1,'張無忌',null),(2,'楊逍',1),(3,'範遙',2),(4,'殷天正',2),(5,'韋一笑',2); Query OK, 5 rows affected (0.00 sec) Records: 5 Duplicates: 0 Warnings: 0 MariaDB [yinzhengjie]> MariaDB [yinzhengjie]> SELECT * FROM emp; +------+-----------+----------+ | id | name | leaderid | +------+-----------+----------+ | 1 | 張無忌 | NULL | | 2 | 楊逍 | 1 | | 3 | 範遙 | 2 | | 4 | 殷天正 | 2 | | 5 | 韋一笑 | 2 | +------+-----------+----------+ rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]> SELECT a.name,b.name AS 領導 FROM emp AS a LEFT OUTER JOIN emp AS b ON a.leaderid = b.id; #同一張表查詢數據，查詢每一個人及其領導的姓名。 +-----------+-----------+ | name | 領導 | +-----------+-----------+ | 楊逍 | 張無忌 | | 範遙 | 楊逍 | | 殷天正 | 楊逍 | | 韋一笑 | 楊逍 | | 張無忌 | NULL | +-----------+-----------+ 5 rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]>
三.SELECT語句(單表操做)執行流程
四.小試牛刀(本案例使用3張表，仍基於上面導入的"yinzhengjie_innodb.sql"數據進行演示)
MariaDB [yinzhengjie]> SELECT * FROM students; +-------+---------------+-----+--------+---------+-----------+ | StuID | Name | Age | Gender | ClassID | TeacherID | +-------+---------------+-----+--------+---------+-----------+ | 1 | Shi Zhongyu | 22 | M | 2 | 3 | | 2 | Shi Potian | 22 | M | 1 | 7 | | 3 | Xie Yanke | 53 | M | 2 | 16 | | 4 | Ding Dian | 32 | M | 4 | 4 | | 5 | Yu Yutong | 26 | M | 3 | 1 | | 6 | Shi Qing | 46 | M | 5 | NULL | | 7 | Xi Ren | 19 | F | 3 | NULL | | 8 | Lin Daiyu | 17 | F | 7 | NULL | | 9 | Ren Yingying | 20 | F | 6 | NULL | | 10 | Yue Lingshan | 19 | F | 3 | NULL | | 11 | Yuan Chengzhi | 23 | M | 6 | NULL | | 12 | Wen Qingqing | 19 | F | 1 | NULL | | 13 | Tian Boguang | 33 | M | 2 | NULL | | 14 | Lu Wushuang | 17 | F | 3 | NULL | | 15 | Duan Yu | 19 | M | 4 | NULL | | 16 | Xu Zhu | 21 | M | 1 | NULL | | 17 | Lin Chong | 25 | M | 4 | NULL | | 18 | Hua Rong | 23 | M | 7 | NULL | | 19 | Xue Baochai | 18 | F | 6 | NULL | | 20 | Diao Chan | 19 | F | 7 | NULL | | 21 | Huang Yueying | 22 | F | 6 | NULL | | 22 | Xiao Qiao | 20 | F | 1 | NULL | | 23 | Ma Chao | 23 | M | 4 | NULL | | 24 | Xu Xian | 27 | M | NULL | NULL | | 25 | Sun Dasheng | 100 | M | NULL | NULL | +-------+---------------+-----+--------+---------+-----------+ 25 rows in set (0.00 sec) MariaDB [yinzhengjie]>
MariaDB [yinzhengjie]> SELECT * FROM courses; +----------+----------------+ | CourseID | Course | +----------+----------------+ | 1 | Hamo Gong | | 2 | Kuihua Baodian | | 3 | Jinshe Jianfa | | 4 | Taiji Quan | | 5 | Daiyu Zanghua | | 6 | Weituo Zhang | | 7 | Dagou Bangfa | +----------+----------------+ 7 rows in set (0.01 sec) MariaDB [yinzhengjie]>
MariaDB [yinzhengjie]> SELECT * FROM scores; +----+-------+----------+-------+ | ID | StuID | CourseID | Score | +----+-------+----------+-------+ | 1 | 1 | 2 | 77 | | 2 | 1 | 6 | 93 | | 3 | 2 | 2 | 47 | | 4 | 2 | 5 | 97 | | 5 | 3 | 2 | 88 | | 6 | 3 | 6 | 75 | | 7 | 4 | 5 | 71 | | 8 | 4 | 2 | 89 | | 9 | 5 | 1 | 39 | | 10 | 5 | 7 | 63 | | 11 | 6 | 1 | 96 | | 12 | 7 | 1 | 86 | | 13 | 7 | 7 | 83 | | 14 | 8 | 4 | 57 | | 15 | 8 | 3 | 93 | +----+-------+----------+-------+ 15 rows in set (0.00 sec) MariaDB [yinzhengjie]>
1>.查詢學生姓名，考試科目以及對應的成績
MariaDB [yinzhengjie]> SELECT a.name AS 姓名,c.course AS 課程,b.score AS 分數 FROM students AS a INNER JOIN scores AS b ON a.stuid = b.id INNER JOIN courses AS c ON b.courseid = c.courseid; +---------------+----------------+--------+ | 姓名 | 課程 | 分數 | +---------------+----------------+--------+ | Shi Zhongyu | Kuihua Baodian | 77 | | Shi Potian | Weituo Zhang | 93 | | Xie Yanke | Kuihua Baodian | 47 | | Ding Dian | Daiyu Zanghua | 97 | | Yu Yutong | Kuihua Baodian | 88 | | Shi Qing | Weituo Zhang | 75 | | Xi Ren | Daiyu Zanghua | 71 | | Lin Daiyu | Kuihua Baodian | 89 | | Ren Yingying | Hamo Gong | 39 | | Yue Lingshan | Dagou Bangfa | 63 | | Yuan Chengzhi | Hamo Gong | 96 | | Wen Qingqing | Hamo Gong | 86 | | Tian Boguang | Dagou Bangfa | 83 | | Lu Wushuang | Taiji Quan | 57 | | Duan Yu | Jinshe Jianfa | 93 | +---------------+----------------+--------+ 15 rows in set (0.00 sec) MariaDB [yinzhengjie]> MariaDB [yinzhengjie]>
2>.以ClassID分組，顯示每班的同窗的人數
3>.以Gender分組，顯示其年齡之和
4>.以ClassID分組，顯示其平均年齡大於25的班級
5>.以Gender分組，顯示各組中年齡大於25的學員的年齡之和
6>.顯示前5位同窗的姓名、課程及成績
7>.顯示其成績高於80的同窗的名稱及課程
8>.取每位同窗各門課的平均成績，顯示成績前三名的同窗的姓名和平均成績
9>.顯示每門課程課程名稱及學習了這門課的同窗的個數
10>.顯示其年齡大於平均年齡的同窗的名字
11>.顯示其學習的課程爲第一、2，4或第7門課的同窗的名字
12>.顯示其成員數最少爲3個的班級的同窗中年齡大於同班同窗平均年齡的同窗
13>.統計各班級中年齡大於全校同窗平均年齡的同窗
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