一、控制用户存取 1、创建修改用户Creating Users Create/alter user new_user identified by password; 例:create user user_1 indentified by pwd_1 alter user user_1 identified by pwd_2 2、给用户授予权限 grant privilege[,privilege] to u..
组合集总计: group by with rollup/cube grouping sets 子查询按执行方式分:标准子查询、关联子查询 标准子查询:嵌套子查询 标量值查询 case with then 使用exits查询 select user_id,user_name from tb_001 tb where [not] exists (select 'x' ..