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Mysql database operation
2022-07-06 03:05:00 【_ half past seven】
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";
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
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