sql-server - 如果满足条件，则 SQL Server 离开连接

Question

我的查询有问题。仅当条件为真时，我才必须执行左外连接。如果条件为假，则执行另一个左外连接。

我试过这个但没有成功:

select 
    * 
from 
    works with(nolock) 
if work.type = 1 
begin
    left outer join 
        users with(nolock) on users.id = work.owner
else
    left outer join 
        groups with(nolock) on groups.id = work.owner
end

我该如何解决这个问题？

Answer 1

你应该尝试左连接它们，但在选择内部，根据用例选择你想要的。

SELECT
  *, 
  CASE work.type WHEN '1' THEN 'a.owner' ELSE 'b.owner' END AS owner
FROM
  blahblah
  left join users on blahblah.user_id = users.id as a,
  left join groups as blahblah.groups_id = groups.id as b