MySQL common syntax

Show which databases there are: show databases;

Create database: create database database1;

Delete database: drop database database1;

Use database: use database1;

View the table: show tables;

Create a new table: create table table1(

id int(10) not null primary key auto increment,

a varchar (20),

b int(10),

c varchar(10) default 'Male',

d int(10)

) ;

View table structure: desc student;

Delete table: drop table student;

Delete primary key: alter table table1 drop primary key;

Add primary key: alter table table1 add primary key(id);

Delete field:alter table table1 drop classid;

Add field:alter table table1 add classid int(10);

Add records: insert into table1(a,b,c,d) values('haha',1,'Hello',2);

Delete: delete from table1 where b = 1;

Modify: update table1 set a = 'hahaha' where b=1;

Wildcard %: multiple arbitrary characters_: one Characters

update table1 set b = 2 where name like '%i%';

Query:

select * from table1;

select id,name from table1;

select * from table1 where b like '%i%';

Sort default ascending order asc descending order desc

select * from table1 order by a asc;

select * from table1 order by a desc;

select * from table1 order by a desc,b asc;

Group function min max count avg

select count(*) from table1;

select min(a) from table1;

select avg(a) from table1;

select max(a ) from table1;

Group: select classid,avg(b) from table1 group by classid having avg(b)>5;

words as query conditions: select * from table1 where age = (select min(b) from table1);

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