Python full stack - operation of the library

1. System database

　　After installing the database system, the system comes with a database. After connecting to the database system through the mysql client, use the show command to view all the libraries that exist in the system:

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| course             |
| course_db          |
| db1 |
| education          |
| mysql              |
| performance_schema |
| sakila |
| school             |
| shop               |
| student            |
| test               |
| world              |
+--------------------+
13 rows in set (0.00 sec)　

　　The source and role of each library:　　

information_schema：
    The virtual library does not occupy disk space, and 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 to add 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：
    A test database automatically created by the MySQL database system;
Except for the libraries mentioned above, the rest are user-defined libraries.

2. Library operation

1. Create a library

　　1) Basic grammar

create database 库名 charset utf8;

　　2) Library name naming convention

Naming rules:
    A. The library name can be composed of letters, numbers, underscores, @, # , $; 
    B. The letters are case-sensitive;
    C. The library name is unique and cannot be created repeatedly;
    D. Prohibit the use of keyword naming;
    E. It is forbidden to use number names alone;
    F. The maximum length of the name is 128 characters

　　3) Basic operations

Create the library, and specify the character encoding:
        create database db1 charset utf8;
 Change library information:
        alter database db1 charset gbk;
 Remove the library:
        drop database db1;
 View database information:
        View all library names:
            show databases;
        View the specified library information:
            show create database db1;
        View the current library:
            select database();