Basic SQL statements

There are 3 types of SQL languages:

1 DDL Statement Database definition statement: Database, table, view, index, stored procedure, such as Create DROP ALTER

2 DML Statement Database manipulation language: Insert Delete update query data, insert Delete, update SELECT

3 DCL Statement Database Control Language: for example, to control the access rights of a user grant REMOVE

Action folder (Library):

Increase

Create Database db1 charset UTF8;

Check

Show CREATE Database db1; #查看刚新建的数据库

show databases;

Select Database (); #查看当前库

Change

ALTER DATABASE DB1 CharSet GBK;

By deleting

Drop database db1;

Database type:

INFORMATION_SCHEMA: Virtual library, do not occupy disk space, storage is the database startup parameters, such as user table information, column information, permission information, character information, etc.

Performance_schema:mysql 5.5 begins a new database that collects database server performance parameters, records various events that occur when processing query requests,

Locks and other phenomena

MySQL: Authorization library, access information for primary storage system users

Test:mysql Database System Auto-created test database

Action file (table)

Increase

Use DB1; # switch Libraries

Select Database (); # View your current folder

CREATE TABLE t1 (id int, name char);

CREATE TABLE t2 Select Id,name from T1 # Copy table

Check

Show Create table1;

Show tables;

Desc T1;

Change

ALTER TABLE T1 modify name char (6);

ALTER TABLE t1 change name name char (7);

By deleting

drop table T1;

Manipulate file contents (record)

Increase

Insert T1 (Id,name) VALUES (1, ' Egon1 '), (2, ' egon2 ');

Check

Select Id,name from Db1.t1;

SELECT * from Db1.t1\g; # when the \g record is more, the line break shows

Change

Update db1.t1 set name= ' SB ' where id=2;

By deleting

Delete from T1 where id=2;

Basic SQL statements