show语句

SHOW具有许多形式，可提供有关数据库，表，列或有关服务器的状态信息的信息。

SHOW {BINARY | MASTER} LOGS    #显示二进制文件
SHOW BINLOG EVENTS [IN 'log_name'] [FROM pos] [LIMIT [offset,] row_count]
SHOW CHARACTER SET [like_or_where]
SHOW COLLATION [like_or_where]
SHOW [FULL] COLUMNS FROM tbl_name [FROM db_name] [like_or_where]
SHOW CREATE DATABASE db_name　　　　#显示创建数据库语句
SHOW CREATE EVENT event_name　　　　#显示创建事件语句
SHOW CREATE FUNCTION func_name
SHOW CREATE PROCEDURE proc_name
SHOW CREATE TABLE tbl_name　　　　　　#显示创建表　
SHOW CREATE TRIGGER trigger_name
SHOW CREATE VIEW view_name
SHOW DATABASES [like_or_where]　　　　
SHOW ENGINE engine_name {STATUS | MUTEX}  #显示存储引擎
SHOW [STORAGE] ENGINES
SHOW ERRORS [LIMIT [offset,] row_count]
SHOW EVENTS
SHOW FUNCTION CODE func_name
SHOW FUNCTION STATUS [like_or_where]
SHOW GRANTS FOR user　　　　　　　　　　#显示用户权限
SHOW INDEX FROM tbl_name [FROM db_name]
SHOW MASTER STATUS　　　　　　　　　　　　#显示主库状态
SHOW OPEN TABLES [FROM db_name] [like_or_where]
SHOW PLUGINS　　　　　　　　　　#显示插件
SHOW PROCEDURE CODE proc_name
SHOW PROCEDURE STATUS [like_or_where]
SHOW PRIVILEGES　　　　　　　　#查看权限表；
SHOW [FULL] PROCESSLIST
SHOW PROFILE [types] [FOR QUERY n] [OFFSET n] [LIMIT n]
SHOW PROFILES
SHOW RELAYLOG EVENTS [IN 'log_name'] [FROM pos] [LIMIT [offset,] row_count]
SHOW SLAVE HOSTS　　　　#
SHOW SLAVE STATUS [FOR CHANNEL channel]       #查看
SHOW [GLOBAL | SESSION] STATUS [like_or_where]
SHOW TABLE STATUS [FROM db_name] [like_or_where]
SHOW [FULL] TABLES [FROM db_name] [like_or_where]
SHOW TRIGGERS [FROM db_name] [like_or_where]
SHOW [GLOBAL | SESSION] VARIABLES [like_or_where]
SHOW WARNINGS [LIMIT [offset,] row_count]

like_or_where: {
    LIKE 'pattern'
  | WHERE expr
}

show index from table  #显示表的索引信息，主要字段Cardinality显示索引中不重复记录数量的预估值。