Tutorial on principles and applications of database system (051) -- MySQL query (XIII): using queries in DML statements

Database system principle and Application Tutorial （051）—— MySQL Inquire about （ 13、 ... and ）：DML Use queries in statements

DML Statement can increase the data in the table 、 Delete 、 Change operation .DML Statement with the help of SELECT Inquire about , It can realize some complex operations .

One 、INSER INTO Statements use SELECT Inquire about

When inserting a record , You can put a SELECT The result of the query is inserted into the data table .

The syntax is as follows ：

INSERT INTO  Table name ( Name 1,  Name 2, ...) 
SELECT  sentence ;

for example ： Create data table stu_age, The table structure is as follows ：

/* Create Table stu_age ( s_id char(5) primary key, s_name char(20), gender char(1), age int ); */
mysql> Create Table stu_age (
    ->     s_id char(5) primary key,
    ->     s_name char(20),
    ->     gender char(1),
    ->     age int
    -> );
Query OK, 0 rows affected (0.01 sec)

Perform the following query , Insert the query results stu_age In the table ：

/* insert into stu_age select s_id,s_name,gender,year(now())-year(birth) from student where gender = ' male '; */
mysql> insert into stu_age
    -> select s_id,s_name,gender,year(now())-year(birth)
    -> from student where gender = ' male ';
Query OK, 8 rows affected (0.01 sec)
Records: 8  Duplicates: 0  Warnings: 0

mysql> select * from stu_age;
+-------+-----------+--------+------+
| s_id  | s_name    | gender | age  |
+-------+-----------+--------+------+
| S2011 |  Zhang Xiaogang     |  male      |   23 |
| S2013 |  Cao mengde     |  male      |   24 |
| S2022 |  Zhou Huajian     |  male      |   23 |
| S2023 |  trump     |  male      |   23 |
| S2024 |  Obama     |  male      |   22 |
| S2025 |  Zhou Jianhua     |  male      |   22 |
| S2026 |  Zhang Xueyou     |  male      |   24 |
| S2032 |  Vinci     |  male      |   23 |
+-------+-----------+--------+------+
8 rows in set (0.00 sec)

Two 、DELETE FROM Statements use SELECT Inquire about

Can be in DELETE Ordered WHERE Clause , Delete records that meet the given conditions .

The syntax is as follows ：

DELETE FROM  Table name  
WHERE  Name | expression   Operator  (SELECT  Inquire about );

for example ： There are two tables as follows

mysql> select * from department;
+------+-----------+
| d_id | d_name    |
+------+-----------+
|   11 |  The sales department     |
|   12 |  Logistics Department     |
|   13 |  Production department     |
|   14 |  R & D department     |
+------+-----------+
4 rows in set (0.00 sec)

mysql> select * from employee;
+-------+-----------+--------+------+
| e_id  | e_name    | salary | d_id |
+-------+-----------+--------+------+
| 11001 |  Zhang Yun       |   4500 |   11 |
| 11002 |  Liu tao       |   4800 |   11 |
| 11003 |  Faye Wong       |   5200 |   11 |
| 12001 |  Liu Jing       |   6200 |   12 |
| 12002 |  Zhang Hong       |   5100 |   12 |
| 12003 |  Chen Gang       |   6800 |   12 |
| 12004 |  Li Zhonghua     |   4200 |   12 |
| 13001 |  Zhou Tao       |   7400 |   13 |
| 13002 |  Zhang Qiang       |   6800 |   13 |
| 13003 |  Zhou long       |   6250 |   13 |
| 13004 |  Zhang Zhongwei     |   4520 |   13 |
+-------+-----------+--------+------+
11 rows in set (0.00 sec)

Delete 【 The sales department 】 All employee information for , The order is as follows ：

/* delete from employee where d_id = ( select d_id from department where d_name = ' The sales department ' ); */
mysql> delete from employee where d_id = (
    ->     select d_id from department where d_name = ' The sales department '
    -> );
Query OK, 3 rows affected (0.08 sec)

mysql> select * from employee;
+-------+-----------+--------+------+
| e_id  | e_name    | salary | d_id |
+-------+-----------+--------+------+
| 12001 |  Liu Jing       |   6200 |   12 |
| 12002 |  Zhang Hong       |   5100 |   12 |
| 12003 |  Chen Gang       |   6800 |   12 |
| 12004 |  Li Zhonghua     |   4200 |   12 |
| 13001 |  Zhou Tao       |   7400 |   13 |
| 13002 |  Zhang Qiang       |   6800 |   13 |
| 13003 |  Zhou long       |   6250 |   13 |
| 13004 |  Zhang Zhongwei     |   4520 |   13 |
+-------+-----------+--------+------+
8 rows in set (0.00 sec)

3、 ... and 、UPDATE Statements use SELECT Inquire about

UPDATE  Table name  
SET  Name  =  expression  
WHERE  Name | expression   Operator  (SELECT  Inquire about );

for example ： There are two tables as follows

mysql> select * from department;
+------+-----------+
| d_id | d_name    |
+------+-----------+
|   11 |  The sales department     |
|   12 |  Logistics Department     |
|   13 |  Production department     |
|   14 |  R & D department     |
+------+-----------+
4 rows in set (0.00 sec)

mysql> select * from employee;
+-------+-----------+--------+------+
| e_id  | e_name    | salary | d_id |
+-------+-----------+--------+------+
| 12001 |  Liu Jing       |   6200 |   12 |
| 12002 |  Zhang Hong       |   5100 |   12 |
| 12003 |  Chen Gang       |   6800 |   12 |
| 12004 |  Li Zhonghua     |   4200 |   12 |
| 13001 |  Zhou Tao       |   7400 |   13 |
| 13002 |  Zhang Qiang       |   6800 |   13 |
| 13003 |  Zhou long       |   6250 |   13 |
| 13004 |  Zhang Zhongwei     |   4520 |   13 |
+-------+-----------+--------+------+
8 rows in set (0.00 sec)

hold 【 Production department 】 The salary of employees increased 50%, The order is as follows ：

/* update employee set salary = salary * 1.5 where d_id = ( select d_id from department where d_name = ' Production department ' ); */
mysql> update employee set salary = salary * 1.5
    -> where d_id = (
    ->     select d_id from department where d_name = ' Production department '
    -> );
Query OK, 4 rows affected (0.01 sec)
Rows matched: 4  Changed: 4  Warnings: 0

mysql> select * from employee;
+-------+-----------+--------+------+
| e_id  | e_name    | salary | d_id |
+-------+-----------+--------+------+
| 12001 |  Liu Jing       |   6200 |   12 |
| 12002 |  Zhang Hong       |   5100 |   12 |
| 12003 |  Chen Gang       |   6800 |   12 |
| 12004 |  Li Zhonghua     |   4200 |   12 |
| 13001 |  Zhou Tao       |  11100 |   13 |
| 13002 |  Zhang Qiang       |  10200 |   13 |
| 13003 |  Zhou long       |   9375 |   13 |
| 13004 |  Zhang Zhongwei     |   6780 |   13 |
+-------+-----------+--------+------+
8 rows in set (0.00 sec)

Four 、 Use UPDATE … JOIN Realize Association update

Use UPDATE … JOIN The command can update the current table with data from another table .

The syntax is as follows ：

update  surface 1 join  surface 2 on  surface 1. Column 1 =  surface 2. Column 2
set  surface 1. Column a =  surface 2. Column b

for example ： There are two tables as follows

mysql> select * from department;
+------+-----------+
| d_id | d_name    |
+------+-----------+
|   11 |  The sales department     |
|   12 |  Logistics Department     |
|   13 |  Production department     |
|   14 |  R & D department     |
+------+-----------+
4 rows in set (0.00 sec)

mysql> select * from employee;
+-------+-----------+--------+------+--------+
| e_id  | e_name    | salary | d_id | d_name |
+-------+-----------+--------+------+--------+
| 12001 |  Liu Jing       |   6200 |   12 | NULL   |
| 12002 |  Zhang Hong       |   5100 |   12 | NULL   |
| 12003 |  Chen Gang       |   6800 |   12 | NULL   |
| 12004 |  Li Zhonghua     |   4200 |   12 | NULL   |
| 13001 |  Zhou Tao       |  11100 |   13 | NULL   |
| 13002 |  Zhang Qiang       |  10200 |   13 | NULL   |
| 13003 |  Zhou long       |   9375 |   13 | NULL   |
| 13004 |  Zhang Zhongwei     |   6780 |   13 | NULL   |
+-------+-----------+--------+------+--------+
8 rows in set (0.00 sec)

according to department In the table d_name Column data update employee In the table d_name Column ：

/* update employee e join department d on e.d_id = d.d_id set e.d_name = d.d_name; */

mysql> update employee e join department d on e.d_id = d.d_id
    -> set e.d_name = d.d_name;
Query OK, 8 rows affected (0.01 sec)
Rows matched: 8  Changed: 8  Warnings: 0

mysql> select * from employee;
+-------+-----------+--------+------+-----------+
| e_id  | e_name    | salary | d_id | d_name    |
+-------+-----------+--------+------+-----------+
| 12001 |  Liu Jing       |   6200 |   12 |  Logistics Department     |
| 12002 |  Zhang Hong       |   5100 |   12 |  Logistics Department     |
| 12003 |  Chen Gang       |   6800 |   12 |  Logistics Department     |
| 12004 |  Li Zhonghua     |   4200 |   12 |  Logistics Department     |
| 13001 |  Zhou Tao       |  11100 |   13 |  Production department     |
| 13002 |  Zhang Qiang       |  10200 |   13 |  Production department     |
| 13003 |  Zhou long       |   9375 |   13 |  Production department     |
| 13004 |  Zhang Zhongwei     |   6780 |   13 |  Production department     |
+-------+-----------+--------+------+-----------+
8 rows in set (0.00 sec)