Question

到目前为止，这是我的查询：

选择
          posts.title
          ，SUM（CASE comments.status WHEN'批准'那么1结束）作为commentsCount
          来自帖子
          INNER JOIN评论
              ON comments.postID = posts.id
          WHERE
              posts.status =？
          GROUP BY               posts.title
          订购单               commentsCount DESC
          限制5

我需要让它在comment.flagged获得commentsCount时检查CASE = 0。我尝试在SUM()调用中添加其他{{1}}，但这会导致致命错误。我怎样才能做到这一点？

谢谢！

Answer 1

SELECT
posts.title
, SUM(IF ((comments.status='approved' AND  comments.flagged = 0),1,0)) AS commentsCount
FROM posts
INNER JOIN comments
ON comments.postID = posts.id
WHERE
posts.status = ?
GROUP BY
posts.title
ORDER BY
commentsCount DESC
LIMIT 5

Answer 2

看起来你真正想做的就是：

SELECT
posts.title
, COUNT(*) AS commentsCount
FROM posts
INNER JOIN comments
ON comments.postID = posts.id
AND comments.status = 'approved'
AND comments.flagged = 0
WHERE
posts.status = ?
GROUP BY
posts.title
ORDER BY
commentsCount DESC
LIMIT 5

由于您只对comments为status的{{1}}感兴趣，因此条件应处于加入条件。

编辑：我已更新了该查询，假设您要计算'approved'为status且'approved'等于flagged的评论。

Answer 3

基于Josh Davis的SQL，这对我有用：

选择
          posts.title
          ，posts.slug
          ，COUNT（comments.id）AS commentsCount
          来自帖子
          INNER JOIN评论
          ON comments.postID = posts.id
          AND comments.status ='已批准'           AND comments.flagged = 0
          WHERE
          posts.status =？
          GROUP BY           posts.title
          订购单           commentsCount DESC
          限制5

如何为此查询添加其他条件（使用CASE）？

3 个答案: