Question

我有一个名为team

的表

我需要选择一名也可能是球队球员的教练......

表的属性是（teamID，playerID，角色）

我可以选择所有教练或所有球员，但不知道如何选择一个......

select *
from isPlaying h
where h.role= 'Coach';

由于

Answer 1

select playerID
from isPlaying coach join isPlaying player on
   coach.playerID = player.playerID
where
   coach.role = 'Coach' and
   player.role = 'Player'

Answer 2

Select * 
from isplaying 
where playerid in (
                   Select playerid 
                   from playerid 
                   where role="coach"
                   );

这是一个嵌套查询。

Answer 3

快速而肮脏的方法是：

select *
from isPlaying h
where h.role = 'Player'
and h.playerID in 
 (select playerID from isPlaying where h.role = 'Coach')

这是假设一名教练不能为一支不同于他教练的球队效力。

Answer 4

SELECT playerID
  FROM isPlaying 
 WHERE role = 'Coach'
INTERSECT
SELECT playerID
  FROM isPlaying 
 WHERE role = 'Player';

SQL查询帮助加入

4 个答案: