Question

表pcKeyword kwId |关键字

表格proPhrase kwId |表决

表格ContraPhrase kwId |表决

因此，投票列是一个整数，我想为指定的关键字求和像这样：

exampleKeyword | 12 | 47

现在我有了这个，但我没有正常工作：

    SELECT pcKeyword.kwId, pcKeyword.keyword, SUM( proPhrase.vote ) AS proVotes, SUM( contraPhrase.vote ) AS contraVotes
FROM pcKeyword
INNER JOIN proPhrase ON proPhrase.kwId = pcKeyword.kwId
INNER JOIN contraPhrase ON contraPhrase.kwId = proPhrase.kwId
GROUP BY pcKeyword.keyword ORDER BY pcKeyword.keyword ASC

Answer 1

你可以尝试：

SELECT kwId, keyword, proVotes, contraVotes
FROM pcKeyword
INNER JOIN ( SELECT kwId pid, SUM( vote ) proVotes  
             FROM proPhrase GROUP BY kwId )  p ON pid = kwId
INNER JOIN ( SELECT kwId cid, SUM( vote ) contraVotes
             FROM contraPhrase GROUP BY kwId ) c ON cid = kwId

这样，您只能在派生表中进行一次分组，而不是经常进行分组！（通过将表分成它们的派生表，我也可以整理整个语法，因为现在列名在每个派生表表达式中都是唯一的。）

见这里：http://sqlfiddle.com/#!2/70634/1

修改

为了完整起见，此处包含LEFT JOIN和COALESCE()的版本，以确保您在没有投票的情况下获得有意义的结果：

SELECT kwId, keyword, COALESCE(proVotes,0) proVotes, COALESCE(contraVotes,0) contraVotes FROM pcKeyword LEFT JOIN ( SELECT kwId pid, SUM( vote ) proVotes FROM proPhrase GROUP BY kwId ) p ON pid = kwId LEFT JOIN ( SELECT kwId cid, SUM( vote ) contraVotes FROM contraPhrase GROUP BY kwId ) c ON cid = kwId

SQLfiddle：http://sqlfiddle.com/#!2/ec51cb/1

双INNER JOIN和SUM

1 个答案: