替代/替代工會與單個連接Select語句

Question

我的表叫posts，我想retrieve所有滿足在select statement以下條件records，並返回一個single table -

select ID from posts where UserID= 23487 and postlevel <> 1 
select ID from posts where ParentID in (select ID from posts where UserID= 23487 and postlevel <> 1) 

現在，使用操作者UNION象下面我可以返回單個表 -

select ID from posts where UserID= 23487 and postlevel <> 1 
UNION 
select ID from posts where ParentID in (select ID from posts where UserID= 23487 and postlevel <> 1) 

輸出

嘗試以下JOIN查詢，但並沒有得到預期的結果，並返回NULL -

select ID from posts cs 
LEFT JOIN posts cs1 ON cs.ID = cs1.ID 
where cs.UserID = 23487 and cs.PostLevel <>1 and cs.ParentID = cs1.ID 

預計

我想獲取使用JOIN或使用單記錄SELECT而不是UNION以獲得如上所示的所需輸出。

Answer 1

你有沒有嘗試過或運算在一起，這兩個條件中的一個WHERE條款：

select ID 
from posts 
where 
    (UserID = 23487 and postlevel <> 1) or 
    (ParentID in (select ID from cs_posts where UserID= 23487 and postlevel <> 1)) 

Answer 2

你可以試試這個

select ID 
from posts 
where 
    (UserID = 23487 and postlevel <> 1) or 
    (EXISTS (select 1 from cs_posts where UserID= 23487 and postlevel <> 1 and ID = ParentID)) 

Answer 3

沒必要工會或存在或....試試這個：

select distinct F1.id from post F1 inner join 
posts f2 on f2.UserID= 23487 and f2.postlevel <> 1 AND 
(F1.id=f2.id or F1.parentid=f2.id) 

如果你想保留重複值刪除不同的