Question

我正在尝试加入3个表格 - e，wp，l

位置为l：name | id | workplace_id

工作场所为wp：name | id

员工e：name | id | location_id | coordinator

我想： 如果WORKPLACE在任何位置有COORDINATOR（协调员= 1）获取该工作场所的所有位置

这似乎不起作用 - 它返回了协调员= 1的工作场所的所有位置，但如果任何工作场所位置的协调员= 1，我需要工作场所的所有位置。

select distinct w.* 
from workplaces as w, 
    (select distinct l.* 
     from locations as l, employees as e 
     where e.location_id = l.id and e.coordinator = 1) as tmp 
where tmp.workplace_id = w.id

Answer 1

select distinct l.* 
from locations as l, workplaces as w, 
    (select distinct l.* 
     from locations as l, employees as e 
     where e.location_id = l.id and e.coordinator = 1) as tmp 
where l.workplace_id = w.id
and tmp.workplace_id = w.id

这就是你要找的东西吗？

Answer 2

首先，子查询是一个非常糟糕的主意，为了进行连接，您应该使用以下任何一种：内连接，左连接或右连接。那么你可以这样：

SELECT l.* FROM locations as l
INNER JOIN workplaces w ON l.workplace_id = w.id
INNER JOIN employees e ON l.id = e.location_id
WHERE e.coordinator = 1;

将3个sql表与/之间的查询连接起来

2 个答案: