如何在mysql搜索JOIN查询期间检查行是否存在？

Question

我有这个有效的sql搜索查询，但仅当投票表中存在投票时才有效。

mysql_query("SELECT m.Title, r.Subject, SUM(v.IsGood) AS Good, SUM(v.IsBad) AS Bad
    FROM Movies m
        JOIN Reviews r
            ON m.ID=r.MovieID
        JOIN Votes v
        ON r.ID=v.ReviewID
    WHERE (m.Title LIKE '%" . $search . "%' OR r.Subject LIKE '%" . $search . "%')
        GROUP BY m.Title, r.Subject
    ORDER BY SUM(v.IsGood) DESC, SUM(v.IsBad) ASC LIMIT 10")

因此，我将其更改为以下内容，以便无论是否有0票，它都应该仍然显示。 但这并没有取得任何结果，有人可以告诉我我做错了什么吗？

mysql_query("SELECT m.Title, r.Subject, COUNT(v.ReviewID) AS Rvotes, SUM(v.IsGood) AS Good, SUM(v.IsBad) AS Bad
    FROM Movies m
        JOIN Reviews r
            ON m.ID=r.MovieID
        JOIN Votes v
        ON r.ID=v.ReviewID
    WHERE (m.Title LIKE '%" . $search . "%' OR r.Subject LIKE '%" . $search . "%')
        GROUP BY m.Title, r.Subject, v.ReviewID
            HAVING Rvotes >= 0
    ORDER BY SUM(v.IsGood) DESC, SUM(v.IsBad) ASC LIMIT 10")

Answer 1

假设即使在投票表中不存在投票的情况下也要获得结果，请LEFT JOIN 投票表。

mysql_query("SELECT m.Title, r.Subject, SUM(v.IsGood) AS Good, SUM(v.IsBad) AS Bad
    FROM Movies m
        JOIN Reviews r
            ON m.ID=r.MovieID
        LEFT JOIN Votes v
        ON r.ID=v.ReviewID
    WHERE (m.Title LIKE '%" . $search . "%' OR r.Subject LIKE '%" . $search . "%')
        GROUP BY m.Title, r.Subject
    ORDER BY SUM(v.IsGood) DESC, SUM(v.IsBad) ASC LIMIT 10")

注意：我已经修改了您的初始查询（不是第二个查询），因为您说它仍然没有提供您想要的内容。