Mysql database operation

Mysql Basic operation

1、 Connect to database

Get into mysql Of bin Enter in the address bar under the directory cmd

Enter the command ：

mysql -u root -p

  After that “ Enter password: ” A hint of , Enter the password to log in

 2、 Displays all databases in the system

Enter the command

show databases;

  Most of the sql The commands have semicolons （;） As an end sign

3、 New database abc

command ：

create database abc;

After the creation is successful, use the following command to view the results

show databases;

 4、 Using a database abc

command ：

use abc;

 5、 In the database abc Create a table aaa

command ：

create table aaa(id int(10),name varchar(20),username varchar(20),password varchar(20),age int(3));

 6、 Add data to the table

increase 8 Data ：

command ：

insert into aaa(id,name,username,password,age) values(1,"zhao","111","zhao111",25);

insert into aaa(id,name,username,password,age) values(2,"qian","222","qian222",27);

insert into aaa(id,name,username,password,age) values(3,"sun","333","sun333",24);

insert into aaa(id,name,username,password,age) values(4,"li","444","li444",28);

insert into aaa(id,name,username,password,age) values(5,"zhou","555","zhou555",22);

insert into aaa(id,name,username,password,age) values(6,"wu","666","wu666",29);

insert into aaa(id,name,username,password,age) values(7,"zheng","777","zheng777",20);

insert into aaa(id,name,username,password,age) values(8,"wang","888","wang888",21);

  After successful insertion, you can use the following command to view aaa Everything in the table ：

select * from aaa;

 7、 In the table aaa Delete data from

Delete id=5 The data of , command ：

delete from aaa where id=5;

After deleting successfully , View results ：

 8、 Modify table aaa The data of

modify id=3 The data of , Put it password Set to 123456789, command ：

update aaa set password=123456789 where id=3;

After deleting successfully , View results ：

 9、 Query table aaa Data in

Query all the data

select * from aaa;

  Look up id and name Field

select id,name from aaa;

  Inquire about name by zhao Of age

select age from aaa where name="zhao";

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MySQL Advanced operation

1、order by Usage of

（1） take aaa The data in the table is sorted by age from high to low ：

select * from aaa order by age desc;

 （2） take aaa The data in the table are based on name From high to low （z-a） Sort ：

select * from aaa order by name desc;

 2、limit Usage of

The first... In the query table 4 Data

select * from aaa limit 0,4;

  From the query table 2 Bar start ,2 Data

select * from aaa limit 2,2;

 3、union select Usage of

select * from aaa union select 1,2,3,4,5;

The result of this command is ,select * from aaa Query results and select 1,2,3,4,5 The result of stitching

 4、union select combination information_schema database

MySQL5.0 There is a version called information_schema The database of , It stores all the information in the database , It's about MySQL Information about all other databases maintained by the server . Such as database name , Table of database , Data type and access right of table column . and 5.0 There is no .

show databases;

select schema_name from information_schema.schemata;

The result of the two commands is the same , Enter the names of all databases

use abc;

show tables;

select table_name from information_schema.tables where table_schema='abc';

The result of the two commands is the same , It's all output abc Table of database