後臺開發經常使用mysql語句_v1.0

目錄

• 1、基本信息查看
  • 1. 表描述
• 2、表操做
  • 1. 查看建表語句
  • 2.查看錶
  • 3. 建立表
  • 4. 更新表
  • 5. 刪除表
  • 6. 重命名錶
• 3、索引操做
  • 1. 查看索引
  • 2. 建立索引
  • 3. 修改索引
  • 4. 刪除索引
• 4、記錄操做
  • 1. 查詢記錄
  • 2. 添加記錄
  • 3. 更新記錄
  • 4. 刪除記錄

1、基本信息查看

1. 表描述

DESCRIBE `table_name`;

2、表操做

1. 查看建表語句

SHOW CREATE TABLE `table_name`;

2.查看錶

SHOW TABLES;

3. 建立表

CREATE TABLE `table_name` (
  `c_id` int(11) unsigned NOT NULL AUTO_INCREMENT COMMENT '惟一ID',
  `c_is_deleted` tinyint(1) NOT NULL DEFAULT '0' COMMENT '邏輯刪除',
  `c_update_time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP COMMENT '更新時間',
  `c_create_time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP COMMENT '建立時間',
  PRIMARY KEY (`c_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COMMENT='table_name'

CREATE TABLE IF NOT EXISTS `table_name` (
  `c_id` bigint(20) unsigned NOT NULL COMMENT '惟一ID',
  `c_uid` char(11) NOT NULL DEFAULT '' COMMENT 'uid列',
  `c_char` char(11) NOT NULL DEFAULT '' COMMENT 'char列',
  `c_varchar1` varchar(30) NOT NULL DEFAULT '' COMMENT 'varchar列',
  `c_varchar2` varchar(300) CHARACTER SET utf8mb4 NOT NULL DEFAULT '' COMMENT 'varchar列，單獨設置字符集',
  `c_text` text CHARACTER SET utf8mb4 NOT NULL COMMENT 'text列，單獨設置字符集',
  `c_tinyint` tinyint(1) NOT NULL DEFAULT '0' COMMENT 'tinyint，當枚舉用(0A 1B 2C)',
  `c_enum` enum('0','1') NOT NULL DEFAULT '0' COMMENT 'enum，枚舉用',
  `c_json` json NOT NULL COMMENT 'json類型列',
  `c_is_deleted` tinyint(1) NOT NULL DEFAULT '0' COMMENT '邏輯刪除',
  `c_update_time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP COMMENT '更新時間',
  `c_create_time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP COMMENT '建立時間',
  PRIMARY KEY (`c_id`),
  KEY `inx_c_uid` (`c_uid`) USING BTREE,
  UNIQUE KEY `udx_c1_c2` (`c_char`,`c_tinyint`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COMMENT='table_name';

4. 更新表

• 增長列

ALTER TABLE `table_name` ADD `c_column` tinyint(1) not null DEFAULT 0 COMMENT '新增列';

• 修改列

ALTER TABLE `table_name` MODIFY COLUMN `c_varchar1` VARCHAR ( 300 ) NOT NULL DEFAULT '' COMMENT '標識符' AFTER `c_varchar2`;

• 刪除列

ALTER TABLE `table_name` DROP COLUMN `c_column`;

5. 刪除表

DROP TABLE if EXISTS `table_name`;

6. 重命名錶

RENAME TABLE `table_name` TO `table_name_2`;

3、索引操做

1. 查看索引

SHOW INDEX FROM table_name [FROM db_name]

2. 建立索引

• 語法

CREATE [UNIQUE|FULLTEXT|SPATIAL] INDEX index_name
[USING index_type]
ON table_name (index_col_name, ...)

CREATE UNIQUE INDEX idx_uid ON `table_name` (`c_uid`);

-- TEXT和BLOB要指定長度
CREATE UNIQUE INDEX idx_text ON `table_name` (`c_text`(6));

• ALTER TABLE方式

ALTER TABLE table_name
ADD [UNIQUE|FULLTEXT|SPATIAL] INDEX index_name (index_col_name,...) [USING index_type]

ALTER TABLE `table_name` ADD PRIMARY KEY ( `c_uid` )

ALTER TABLE `table_name` ADD INDEX `udx_c1_c2` ( `c_char`(n), `c_tinyint` ) USING BTREE;

3. 修改索引

ALTER TABLE `table_name` DROP INDEX `udx_c1_c2`,
ADD INDEX `udx_c1_c2` ( `c_char`, `c_tinyint`, `c_is_deleted` ) USING HASH;

4. 刪除索引

ALTER TABLE table_name DROP PRIMARY KEY;

DROP INDEX `idx_name` ON `table_name`;

ALTER TABLE `table_name` DROP INDEX `udx_c1_c2`;

4、記錄操做

1. 查詢記錄

• 簡單查詢

子句順序：SELETC、 FROM、 WHERE、 GROUP BY、 HAVING、 ORDER BY、 LIMIT

SELECT * FROM table_name WHERE ... ORDER BY c_column1,c_column2 DESC;

• 模糊查詢
  特殊字符要轉義% _

SELECT * FROM table_name WHERE c_column LIKE CONCAT('first','second','third');

SELECT * FROM table_name WHERE c_column LIKE CONCAT('%','_','%');

• 分組查詢

  WHERE過濾行, HAVING過濾分組

SELECT GROUP_CONCAT(c_column) FROM table_name WHERE c_is_deleted=0 GROUP BY c_column1, c_column2 HAVING COUNT(c_column3) >= 2;

-- 可能報錯：incompatible with sql_mode=only_full_group_by
SELECT GROUP_CONCAT(c_column) FROM table_name WHERE c_is_deleted=0 GROUP BY c_column1, c_column2 HAVING COUNT(c_column3) >= 2 ORDER BY c_order DESC;

SELECT GROUP_CONCAT(c_id),COUNT(*) FROM table_name GROUP BY c_type WITH ROLLUP;

• 分頁查詢

  檢索出來的第一行爲行0而不是行1。

-- 查詢兩條記錄，開始行1
SELECT * FROM table_name LIMIT 1, 2;

• 計算字段和函數

（1）計算字段

SELECT 1+1 AS result;

SELECT CONCAT('first', c_column, 'third') AS c_alias_name FROM table_name;

SELECT CONCAT('first', TRIM(c_column), 'third') AS c_alias_name FROM table_name;

（2）處理函數

SELECT UUID() AS `uid`;

SELECT UPPER('a');

SELECT DATE(c_create_time) AS `date`, TIME(c_create_time) AS `time` FROM table_name;

（3）彙集函數

SELECT COUNT( * ),
         MIN( c_column ),
         MAX( c_column ),
         AVG( c_column ) 
FROM table_name;

SELECT SUM( c_column1 * c_column2 ) 
FROM table_name;

• 子查詢

SELECT * 
FROM table_name1 
WHERE c_column IN ( SELECT c_column 
                    FROM table_name2
                    WHERE c_is_deleted = 1 );
                    
-- 計算字段做爲子查詢
SELECT table_name1.c_name,
    ( SELECT COUNT( * ) 
      FROM table_name2 
      WHERE table_name2.c_key = table_name1.c_key ) AS nums
FROM table_name1 
WHERE c_is_deleted = 0;

• 聯結查詢

(1) 自聯結

SELECT t1.c_id, t1.c_name 
FROM table_name AS t1, table_name AS t2 
WHERE t1.c_id = t2.c_id 
AND t2.c_key = '';

(2) 天然聯結

SELECT t1.c_id, t1.c_name 
FROM table_name1 AS t1, table_name2 AS t2 
WHERE t1.c_id = t2.c_id 
AND t2.c_key = '';

(3) 外部聯結

SELECT
    table_name1.c_id,
    table_name1.c_name,
    table_name2.c_name 
FROM table_name1
LEFT JOIN table_name2 ON table_name2.c_key = table_name1.c_key
WHERE ...;

• 查詢結果case when then else end用法

(1) 語法

--簡單Case函數 
CASE sex 
    WHEN '1' THEN '男' 
    WHEN '2' THEN '女' 
    ELSE '其餘' 
END

--Case搜索函數, 
CASE 
    WHEN sex = '1' THEN '男' 
    WHEN sex = '2' THEN '女' 
    ELSE '其餘' 
END

(2) 示例

SELECT `name`,
CASE `name` 
    WHEN 'sam' THEN 'yong' 
    WHEN 'lee' THEN 'handsome' 
    ELSE 'good' 
END AS `alias` 
FROM `table_name`;

SELECT `name`,
CASE
    WHEN birthday < '1981' THEN 'old' 
    WHEN birthday > '1988' THEN 'yong' 
    ELSE 'ok' 
END AS `yorn` 
FROM `table_name`;

2. 添加記錄

• 簡單插入

INSERT INTO table_name ( column1, column2 ) VALUES ( value1, value2 );

• 批量插入

INSERT INTO table_name 
    ( column1, column2 )
VALUES
    ( value1, value2 ),
    ( value1, value2 );

• INSERT SELECT插入

INSERT INTO table_name ( column1, column2 )
    SELECT column1, column2 
    FROM table_name 
    WHERE c_id=1;

3. 更新記錄

UPDATE `table_name` 
SET 
    `c_varchar1` = 'string',
    `c_update_time` = CURRENT_TIMESTAMP 
WHERE `c_id` = 1;

4. 刪除記錄

• DELETE方式

DELETE FROM `table_name` WHERE `c_id`=1;

• TRUNCATE方式-清空表-慎用

-- 刪除原表再新建表
 TRUNCATE TABLE `table_name`