Mysql database foundation: DML data operation language

DML Language

1、insert Insert statement

grammar

• The first way ： Classic insertion

insert into  Table name ( Name 1, Name 2,...) values ( value 1, value 2,...)

Be careful ：
1、 The type of the inserted value should be consistent with or compatible with the type of the column
2、 Not for null The column of must have a value inserted , It can be for null The column of （nullable） Either null Insert as value , Or you can omit the column and the corresponding value of the column at the same time .
3、 The order of columns can be reversed , But the corresponding value should also be matched and exchanged
4、 The number of columns and the number of values must be the same
5、 You can omit column names , But the order of the columns should be consistent with that of the columns in the table , And the value of null Of cannot be omitted

• The second way

insert into  Table name 
set  Name = value , Name = value ,...

Compare the two insertion methods
1、 Method 1 can support inserting multiple rows , The way 2 I won't support it

insert into  Table name 
values ( value 1, value 2,...)
,( value 1, value 2,...)
,( value 1, value 2...);

2、 Mode 1 supports subquery , Method 2 does not support sub query

insert into  Table name ( Name 1, Name 2,...)
select sentence 

So mode 1 uses more scenarios

2、update to update / Modify the statement

2.1 Record of modification list

• grammar

update  Table name 
set  Column = The new value , Column = The new value ,...
where  filter ;

• example

#  modify beauty The phone number of the girl surnamed Tang in the table is 13887888881
update beauty set phone = '13887888881'
where name like ' The tang dynasty %';

#  modify boys In the table id Number is 2 My name is Zhang Fei , Age is 22
update boys set name = ' Zhang Fei ',age = 22
where id = 2;

2.2 Modify multi table records

• grammar

update  surface 1  Alias 
inner|left|right join  surface 2  Alias 
on  Connection condition 
set  Column = value ,...
where  filter 

• Case study

#  Change Zhang's girlfriend's cell phone number to 114
update boys b
inner join beauty b
on bo.`id`=b.`boyfrind_id`
set b.`phone`='114'
where bo.`boyName`=' zhang wuji ';

3、delete/truncate Delete statements

grammar

• delete sentence

effect ： Delete data from table

1、 Delete single table

#  Delete all data in the table 
delete from  Table name ;
#  Delete the data of the specified condition in the table 
delete from  Table name  where  filter ;

Example ：

#  Delete the phone number to 9 Girl's message at the end 
delete from beauty where phone like '%9';

2、 Delete multiple tables

#  Delete Zhang Wuji's girlfriend's information 
delete  surface 1 Another name for , surface 2 Another name for 
from  surface 1, surface 2
inner|left|right join  surface 2  Alias 
on  Connection condition 
where  filter ;

Example ：

#  Delete Zhang Wuji's girlfriend's information 
delete b
from beauty b
inner join boys bo
on b.`boyfriend_id`=bo.`id`
where bo.`boyName`=' zhang wuji ';

• truncate sentence

effect ： Delete all data in the table

 truncate table  Table name ;

delete and truncate The difference between sentences
1、delete You can add where Conditions ,truncate Cannot add
2、truncate Delete efficiency ratio delete high
3、 If the table to be deleted has a self growing column , If you use delete After deleting , Then insert the data , The value of the self growing column starts at the breakpoint , and truncate After deleting , Then insert the data , The value of the self growing column starts from 1 Start
4、truncate Delete has no return value ,delete Delete with return value
5、truncate Deletion cannot be rolled back ,delete Delete can be rolled back