Question

我有一个查询来获取用户的朋友，还有一个用于获取用户发布的所有帖子作为状态，现在我需要将它们合并。

朋友：

SELECT CASE WHEN userID=$session THEN userID2 ELSE userID END AS friendID 
FROM friends 
WHERE userID=$session OR userID2=$session

然后用户帖子：

SELECT * FROM posts 
WHERE toID=fromID AND state='0' 
ORDER BY id DESC LIMIT 10

所以两者都应该合作。来自第一个查询的friendID应该等于ID或fromID，因为它们都需要相同而无关紧要。

Answer 1

这些帖子的第二个条件是他们来自朋友。所以：

SELECT * FROM posts  
WHERE toID=fromID AND state='0' AND toID IN
    (SELECT CASE WHEN userID=$session THEN userID2 ELSE userID END AS friendID  
     FROM friends  
     WHERE userID=$session OR userID2=$session)
ORDER BY id DESC LIMIT 10

Answer 2

您应该使用JOIN：

SELECT 
    CASE 
        WHEN userID=$session THEN userID2 
        ELSE userID 
    END AS friendID, 
    posts.*
FROM friends 
JOIN posts on posts.toID = friends.friendID
WHERE (userID=$session OR userID2=$session)
AND toID=fromID 
AND state='0' 
ORDER BY id DESC LIMIT 10

结合两个MYSQL查询，仅通过朋友获取帖子

2 个答案: