MySQL Lecture 2: DML Data Operation Statements

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##Article Directory

1. Insert
• 2. Modify update
• 3. Delete delete/truncate
• 4. DML statement exercises

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1. Insert

Method 1:

insert into table name (column name,...) values(value1,...); Method 2:
insert into table name set column name=value, column name=value...

CompareWhether it supports inserting multiple rowsWhether it supports subqueriesMethod 1√×Method 2√×

【插入方式一】# 1.插入的值的类型要与列的类型一致或兼容INSERT INTO beauty(id,NAME,sex,borndate,phone,photo,boyfriend_id)VALUE(13,'双笙','女','1999-02-15','13868666666',NULL,2);# 2.列的顺序可以调换INSERT INTO beauty(NAME,id,sex,borndate,phone,photo,boyfriend_id)VALUE('徐婕',14,'女','1999-02-16','13868666661',NULL,2);# 3.可以省略列名,列的顺序和表中列的顺序一致INSERT INTO beautyVALUE(16,'金克斯','女','2000-02-16','13868666661',NULL,2);# 4.支持子查询INSERT INTO beauty(id,NAME,phone)SELECT id,boyname,'110'FROM boys WHERE id

2. Modify update

1. Modify the record syntax of a single table:

update table name
set column=new value, column=new value,...
where filter condition;

Execution order:

update > where > ; set

2. Modify the record syntax of multiple tables:

update table 1 alias
[inner|left|right] join table 2 alias
on connection condition
set column=new value, column=new value,...
where filter condition;

【修改单表的记录】# 修改beautty表中姓周的女生电话为15888888888UPDATE beautySET phone='15888888888'WHERE NAME LIKE '%周%';【修改多表的记录】# 将张无忌的女朋友的电话号改为2333UPDATE boys b1JOIN beauty b2 
ON b1.id=b2.boyfriend_idSET b2.phone='2333'WHERE b1.boyName='张无忌';

3. Delete delete/truncate

delete

Single table deletion:

delete from table name where filter conditions

Multiple table deletion:

delete table 1 alias, table 2 alias
from table 1 alias
inner|left|right join table 2 alias on connection condition
where filter condition;

truncate

Clear Single table:

truncate table table name;

Note:

There is no return value for truncate deletion, and there is a return value for delete deletion.

ComparisonWhether it is possible to add a where conditionWhether it can be rolled backIs there a return value? EfficiencyWhen there are auto-increasing columns in the table##deletetruncate

【delete】# 1.单表删除# 删除以9结尾的女生信息DELETE FROM beauty WHERE phone LIKE '%9';# 2.多表删除# 删除黄晓明的信息以及他女朋友的信息DELETE b1,b2FROM beauty b1INNER JOIN boys b2ON b1.boyfriend_id=b2.idWHERE b2.boyName='黄晓明';【truncate】# 仅支持单表删除全部数据TRUNCATE TABLE boys;

√	√	√	Generally	Use delete to delete and then insert data. The self-increasing value starts from the breakpoint
×	×	×	is slightly higher than delete	Use truncate to delete and then insert data, which will grow automatically The value starts from 1

4. DML statement exercises

Learned the addition, deletion and modification of DML language statements, Try to complete the following exercises:

Answer:
1. Execute the following sql statement
CREATE TABLE my_employees( Id INT(10),
First_name VARCHAR(10),
Last_name VARCHAR(10),
Userid VARCHAR(10),
Salary DOUBLE(10,2)
);
CREATE TABLE users(
id INT ,
userid VARCHAR(10),
department_id INT
);

2.
DESC my_employees
3.
Method 1: INSERT INTO my_employees
VALUES(1,'patel','Ralph','Rpatel',895),
(2,'Dancs','Betty','Bdancs',860 ),
(3,'Biri','Ben','Bbiri',1100),
(4,'Newman','Chad','Cnewman',750),
(5, 'Ropeburn','Audrey','Aropebur',1550);
TRUNCATE TABLE my_employees;
Method 1:
INSERT INTO my_employees
SELECT 1,'patel','Ralph','Rpatel ',895 UNION
SELECT 2,'Dancs','Betty','Bdancs',860 UNION
SELECT 3,'Biri','Ben','Bbiri',1100 UNION
SELECT 4, 'Newman','Chad','Cnewman',750 UNION
SELECT 5,'Ropeburn','Audrey','Aropebur',1550;

4.
INSERT INTO users VALUE(1,'Rpatel',10),
(2,'Bdancs',10),
(3,'Bbiri',20),
(4,'Cnewman' ,30),
(5,'Aropebur',40);

5.
UPDATE my_employees SET Last_name='drelxer'
WHERE id=3;

6.
UPDATE my_employees SET salary=1000
WHERE salary
7.
DELETE u,e FROM users u
JOIN my_employees e ON u.userid=e.userid
WHERE u.userid='Bbiri';

8.
DELETE FROM my_employees; DELETE FROM users;

9.
SELECT * FROM my_employees; SELECT * FROM users;

10.
TRUNCATE TABLE my_employees;

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