mysql 中show databases 后出现的 INFORMATION_SCHEMA:是什么

 INFORMATION_SCHEMA:
 
用途:访问数据库元数据。
它是以 sysobjects 和 syscolumns 系统表为基础建立的系统视图。它的字段更具备可读性。
它不包含系统数据库的表.
 
系统 INFORMATION_SCHEMA 视图:
INFORMATION_SCHEMA.CHECK_CONSTRAINTS
INFORMATION_SCHEMA.COLUMN_DOMAIN_USAGE
INFORMATION_SCHEMA.COLUMN_PRIVILEGES
INFORMATION_SCHEMA.COLUMNS
INFORMATION_SCHEMA.CONSTRAINT_COLUMN_USAGE
INFORMATION_SCHEMA.CONSTRAINT_TABLE_USAGE
INFORMATION_SCHEMA.DOMAIN_CONSTRAINTS
INFORMATION_SCHEMA.DOMAINS
INFORMATION_SCHEMA.KEY_COLUMN_USAGE
INFORMATION_SCHEMA.PARAMETERS
INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS
INFORMATION_SCHEMA.ROUTINES   返回当前数据库中当前用户能访问的所有函数和存储过程的元数据信息。
INFORMATION_SCHEMA.ROUTINE_COLUMNS
INFORMATION _ SCHEMA.SCHEMATA
INFORMATION_SCHEMA.TABLE_CONSTRAINTS
INFORMATION_SCHEMA.TABLE_PRIVILEGES
INFORMATION_SCHEMA.TABLES
INFORMATION_SCHEMA.VIEW_COLUMN_USAGE
INFORMATION_SCHEMA.VIEW_TABLE_USAGE
INFORMATION_SCHEMA.VIEWS
eg: SELECT * FROM INFORMATION_SCHEMA.TABLES