library operations

1. System database

information_schema: Virtual library, which does not occupy disk space, stores some parameters after the database is started, such as user table information, column information, permission information, character information, etc.
performance_schema: MySQL 5.5 starts a new database: mainly used to collect database server performance parameters, record various events, locks and other phenomena that occur when processing query requests
mysql: Authorization library, which mainly stores the permission information of system users
test: The test database automatically created by the MySQL database system

2. Create a database

1 Syntax (help create database)

CREATE DATABASE database name charset utf8;

2 Database naming rules:

Can be composed of letters, numbers, underscores, @, #, $
case sensitive
uniqueness
Cannot use keywords such as create select
Numbers cannot be used alone
Up to 128 bits

3. Database related operations

1 View database
show databases;
show create database db1;
select database();

2Choose the database
USE database name

3 Delete the database
DROP DATABASE database name;

4 Modify the database
alter database db1 charset utf8;