#查询指定数据库中的表信息
select table_name,table_comment,create_time,engine from information_schema.tables where table_schema = (select database())
-- 查询指定表的信息
select table_name,table_comment,create_time,engine from information_schema.tables where table_schema = (select database()) and table_name = 'user'
/*查指定数据库中有几张表*/
select count(1) from information_schema.tables where table_schema = (select database())
#查询指定表的列信息
select column_name,column_comment,data_type,column_key,extra from information_schema.columns where table_schema = (select database()) and table_name = 'user'