MySQL數據庫管理

上一篇博客咱們介紹了數據庫的一些基本操做，那麼此次就讓咱們一次來認識一下操做數據庫的一些更深刻的方法。

1、視圖

視圖一般分爲三種：

• 簡單視圖，單張表
• 複雜視圖，多張表
• 物化視圖

（1）簡單視圖的建立

mysql> create view v1_students as select name,age from students; Query OK, 0 rows affected (0.01 sec)

（2）複雜視圖的建立

mysql> create view v2_students as select s.name student_name,t.name teacher_name from students s join teachers t on s.teacherid=t.tid; Query OK, 0 rows affected (0.00 sec)

（3）查看指定的視圖信息

mysql> show create view v2_students\G; *************************** 1. row *************************** View: v2_students Create View: CREATE ALGORITHM=UNDEFINED DEFINER=`root`@`localhost` SQL SECURITY DEFINER VIEW `v2_students` AS select `s`.`Name` AS `student_name`,`t`.`Name` AS `teacher_name` from (`students` `s` join `teachers` `t` on((`s`.`TeacherID` = `t`.`TID`))) character_set_client: latin1 collation_connection: latin1_swedish_ci 1 row in set (0.00 sec)

（4）查看全部的視圖信息

MariaDB [hidb]> select * from information_schema.views\G; mysql> select * from information_schema.views\G; *************************** 1. row *************************** TABLE_CATALOG: NULL TABLE_SCHEMA: hellodb TABLE_NAME: v1_students VIEW_DEFINITION: select `hellodb`.`students`.`Name` AS `name`,`hellodb`.`students`.`Age` AS `age` from `hellodb`.`students` CHECK_OPTION: NONE IS_UPDATABLE: YES DEFINER: root@localhost SECURITY_TYPE: DEFINER CHARACTER_SET_CLIENT: latin1 COLLATION_CONNECTION: latin1_swedish_ci *************************** 2. row *************************** TABLE_CATALOG: NULL TABLE_SCHEMA: hellodb TABLE_NAME: v2_students VIEW_DEFINITION: select `s`.`Name` AS `student_name`,`t`.`Name` AS `teacher_name` from (`hellodb`.`students` `s` join `hellodb`.`teachers` `t` on((`s`.`TeacherID` = `t`.`TID`))) CHECK_OPTION: NONE IS_UPDATABLE: YES DEFINER: root@localhost SECURITY_TYPE: DEFINER CHARACTER_SET_CLIENT: latin1 COLLATION_CONNECTION: latin1_swedish_ci 2 rows in set (0.05 sec)

（5）刪除視圖

MariaDB [hidb]> drop view v1_students; Query OK, 0 rows affected (0.00 sec)

（6）更新視圖數據

mysql> update v2_students set teacher_name='Tie Muzhen' where student_name='da ji'; Query OK, 1 row affected (0.00 sec) Rows matched: 1  Changed: 1  Warnings: 0 mysql> select * from teachers; +-----+------------+-----+--------+
| TID | Name       | Age | Gender |
+-----+------------+-----+--------+
|   1 | Liu Bang   |  45 | M      |
|   2 | Ying Zheng |  94 | M      |
|   3 | Wu Zetian  |  77 | F      |
|   4 | Tie Muzhen |  93 | F      |
+-----+------------+-----+--------+
4 rows in set (0.00 sec)

由這個例子咱們能夠看出，修改視圖實際上修改的是基表，那麼須要注意的就是有些狀況下是不能修改視圖的數據的。分爲如下幾種狀況，select字句中不能包含distinct，組函數，union以及group by 等語句。

2、自定義函數

函數有多種，大體分爲自定義和內置函數兩種，內置函數也有不少，不須要定義，可直接進行調用，那麼咱們一塊兒來詳細的認識一下自定義函數的用法。

（1）自定義函數的建立

create +function 而後加函數名 後跟renturn內容便可。

mysql> CREATE FUNCTION simpleFun() RETURNS VARCHAR(20) RETURN "Hello World!"; Query OK, 0 rows affected (0.04 sec)

(2) 查看全部函數信息

mysql> show function status\G; *************************** 1. row *************************** Db: hellodb Name: simpleFun Type: FUNCTION Definer: root@localhost Modified: 2018-09-06 01:31:30 Created: 2018-09-06 01:31:30 Security_type: DEFINER Comment: character_set_client: latin1 collation_connection: latin1_swedish_ci Database Collation: utf8_general_ci 1 row in set (0.00 sec)

（3）查看指定自定義函數的定義

mysql> show create function simplefun\G; *************************** 1. row ***************************
             Function: simplefun sql_mode: Create Function: CREATE DEFINER=`root`@`localhost` FUNCTION `simplefun`() RETURNS varchar(20) CHARSET utf8 RETURN "Hello World!" character_set_client: latin1 collation_connection: latin1_swedish_ci Database Collation: utf8_general_ci 1 row in set (0.00 sec)

（4）帶參自定義函數

mysql> delimiter //    將分割符定義爲// mysql> create function addtwonumber(x smallint unsigned,y smallint unsigned) -> returns smallint begin
     -> declare a,b smallint unsigned; -> set a=x,b=y; -> return a+b; -> end// Query OK, 0 rows affected (0.03 sec) mysql> delimiter ; 從新定義爲； mysql> select addtwonumber(10,20); +-------------------------------+
| addtwonumber(10,20) |
+-------------------------------+
|                  30                    |
+-------------------------------+
1 row in set (0.03 sec)

（5）刪除自定義函數

MariaDB [mysql]> drop function simplefun; Query OK, 0 rows affected (0.00 sec)

3、觸發器trigger

觸發器是基於兩個表之間的聯繫，一個表發生變化觸動觸發器而後引發的另外一個表也發生變化。

先建兩個表

mysql> create table student_info( stu_id int(11) primary key auto_increment, -> stu_name varchar(255) default null); Query OK, 0 rows affected (0.01 sec) create table student_count( student_count int(11) default 0); Query OK, 0 rows affected (0.01 sec) mysql> insert into student_count values(0); Query OK, 1 row affected (0.00 sec) 表的基本操做已完成，接下來就是創建觸發器了。

（1）觸發器建立

mysql> create trigger trigger_student_count_insert after insert on student_info for each row update student_count set student_count=student_count+1; Query OK, 0 rows affected (0.01 sec) 這裏須要注意的是觸發器的名字儘可能起與之相關的，容易看懂。 mysql> insert into student_info values (1,'wsy'); Query OK, 1 row affected (0.00 sec) mysql> select * from student_count; +---------------+
| student_count |
+---------------+
|             1 |
+---------------+
1 row in set (0.00 sec)

（2）查看現有觸發器

mysql> SHOW TRIGGERS\G; *************************** 1. row *************************** Trigger: trigger_student_count_insert Event: INSERT Table: student_info Statement: update student_count set student_count=student_count+1 Timing: AFTER Created: NULL sql_mode: Definer: root@localhost character_set_client: latin1 collation_connection: latin1_swedish_ci Database Collation: utf8_general_ci 1 row in set (0.00 sec)

（3）刪除觸發器

mysql>DROP TRIGGER trigger_student_count_insert;

4、存儲過程

存儲過程：存儲過程保存在mysql.proc表中

（1）建立一個無參存儲過程

mysql> delimiter // mysql> create procedure showtime()  begin  select now();    -> end // Query OK, 0 rows affected (0.00 sec)

 (2)  建立一個含參存儲過程

mysql>create procedure deletebyld(in uid smallint unsigned,out num smallint unsigned)  begin delete from hellodb.students where stuid=uid; select row_count() into num; end// mysql> delimiter ; mysql> call deletebyld(2,@line); Query OK, 0 rows affected (0.02 sec) mysql> select @line; +-------+
| @line |
+-------+
|     1 |
+-------+
1 row in set (0.00 sec)

（2）存儲過程的調用

mysql> call showtime; +---------------------+
| now()               |
+---------------------+
| 2018-09-06 02:15:54 |
+---------------------+
1 row in set (0.00 sec) Query OK, 0 rows affected (0.00 sec)

 

（2）查看指定的存儲過程建立

mysql>show create procedure showtime\G;

（3）刪除存儲過程

mysql> drop procedure showtime;

（4）查看存儲過程列表

mysql> SHOW PROCEDURE STATUS\G; *************************** 1. row *************************** Db: hellodb Name: showtime Type: PROCEDURE Definer: root@localhost Modified: 2018-09-06 02:15:37 Created: 2018-09-06 02:15:37 Security_type: DEFINER Comment: character_set_client: latin1 collation_connection: latin1_swedish_ci Database Collation: utf8_general_ci 1 row in set (0.00 sec)

    (5)存儲過程的優點

• 存儲過程把常常使用的SQL語句或業務邏輯封裝起來,預編譯保存在數據庫中, 當須要時從數據庫中直接調用,省去了編譯的過程 
• 提升了運行速度
• 同時下降網絡數據傳輸量

有關MySQL的相關函數及觸發器內容就介紹到這裏了。