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’ from tb_001 where manager_id=tb.user_id ) 关联更新 update table1 alias1
