数据库名
select group_concat(schema_name) from information_schema.schemata
表名(括号里用来指定数据库名，默认当前数据库，即database())
select group_concat(table_name) from information_schema.tables (where table_schema=[schema_name])
列名
select group_concat(column_name) from information_schema.columns where table_name=[table_name]
