SQL添加的问题

请

我试图在几个不同的统计中获得用户赢得的积分的总价值，但所有内容都来自同一张表

SQL:

问题是，若并没有最佳值（默认值为0，最佳值为1），那个么“总计”和“最佳和”将一无所获。如果用户没有“最佳”，我需要0，以便正确执行计算

对不起，我的英语不好，我想你会理解的

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谢谢

如果best=NULL尝试合并，我假设您想要一个0值

count(COALESCE(best,0) AS best)

您应该使用COALESCE（n.best，0）

当第一个参数为NULL时，COALESCE返回第二个参数

SELECT o.author_id, SUM(o.vote_value) AS vote_value, 
            COALESCE(n.best, 0) AS best_sum, 
            (SUM(o.vote_value) + (10 * COALESCE(n.best, 0))) AS total
            FROM comments o
            LEFT JOIN (
              SELECT COUNT(best) AS best, author_id
              FROM comments
              WHERE best = 1
              GROUP BY author_id
              ) n ON o.author_id = n.author_id
            GROUP BY o.author_id
            ORDER BY total DESC
            LIMIT 0, 4

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我认为您的问题在于，您正在筛选出最佳值不是1的行，因此它们不包括在分组中。试试这个：

SELECT o.author_id, SUM(o.vote_value) AS vote_value, n.best AS best_sum, 
            (SUM(o.vote_value) + (10 * n.best)) AS total
            FROM comments o
            JOIN (
              SELECT SUM(best) AS best, author_id
              FROM comments
              GROUP BY author_id
              ) n ON o.author_id = n.author_id
            GROUP BY o.author_id
            ORDER BY total DESC
            LIMIT 0, 4

另外，也许我遗漏了一些东西，但是保存子查询不是很有效吗

SELECT o.author_id, SUM(o.vote_value) AS vote_value, SUM(o.best) AS best_sum, 
            (SUM(o.vote_value) + (10 * SUM(o.best))) AS total
            FROM comments o
            GROUP BY o.author_id
            ORDER BY total DESC
            LIMIT 0, 4

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我想你只确定了最好的金额。道达尔需要同样的治疗。。。第二个是有效的，不需要子查询：）谢谢，你节省了我的时间：））我认为这不起作用，因为最好的总是1（WHERE子句需要它）。问题来自左连接生成空值，因此如果要使用COALESCE，必须按照sergiom的建议执行。

SELECT o.author_id, SUM(o.vote_value) AS vote_value, SUM(o.best) AS best_sum, 
            (SUM(o.vote_value) + (10 * SUM(o.best))) AS total
            FROM comments o
            GROUP BY o.author_id
            ORDER BY total DESC
            LIMIT 0, 4