使用where子句并设置notnull条件

SELECT u.nickname, tpa.numPosts, tpc.numComments
    FROM Users u
    LEFT JOIN
    (SELECT pa.nickname, COUNT(pa.nickname) AS numPosts
        FROM postAuthors pa
        GROUP BY pa.nickname
    )tpa
    ON u.nickname = tpa.nickname LEFT JOIN 
    (SELECT pc.nickname, COUNT(pc.nickname) AS numComments
        FROM postComments pc
        GROUP BY pc.nickname
    )tpc
    ON u.nickname = tpc.nickname;
   where tpa.nickname is not null or tpc.nickname is not null

您可以通过此条件在页面中显示时控制它。

if(object->property_name==Null && object->property_name==Null ){
 continue;
}

只需添加 WHERE pc.nickname IS NOT NULL OR pa.nickname IS NOT NULL 到查询，即。

SELECT u.nickname, pa.numPosts, pc.numComments
FROM Users u
LEFT JOIN
(SELECT pa.nickname, COUNT(pa.nickname) AS numPosts
    FROM postAuthors pa
    GROUP BY pa.nickname
)pa
ON u.nickname = pa.nickname LEFT JOIN 
(SELECT pc.nickname, COUNT(pc.nickname) AS numComments
    FROM postComments pc
    GROUP BY pc.nickname
)pc
ON u.nickname = pc.nickname
WHERE pc.nickname IS NOT NULL OR pa.nickname IS NOT NULL

这将排除在postauthors和postcomments中都没有值的任何用户。