合并多个表并使用 COALESCE 的奇怪行为

Question

我有一个很大的问题，我一直在努力解决并调整了一段时间。

SELECT 
    tastingNotes.userID, tastingNotes.beerID, tastingNotes.noteID, 
    tastingNotes.note, user.userName, 
    COALESCE(sum(tasteNoteRate.score),0) as `score`
FROM 
    tastingNotes
    INNER JOIN `user` on tastingNotes.userID = `user`.userID 
    LEFT JOIN tasteNoteRate on tastingNotes.noteID = tasteNoteRate.noteID  
WHERE tastingNotes.beerID = 'C5RJc0'
GROUP BY tastingNotes.noteID
ORDER BY score DESC
LIMIT 0,50;

我正在使用 COALESCE(sum(tasteNoteRate.score),0) 给结果返回零值，如果他们还没有分数的话。

奇怪的是，当我应该有两个结果时，它只返回一个分数为零的音符。

然后当我给一个分数时，他们都出现了，一个是它的分数，然后是第二个是零分。

Answer 1

尝试

SELECT q.noteID, q.userID, q.beerID, q.note, q.score, u.userName
  FROM (
  SELECT n.noteID, n.userID, n.beerID, n.note, COALESCE(SUM(r.score), 0) score
    FROM tastingNotes n LEFT JOIN tasteNoteRate r
      ON n.noteID = r.noteID
   WHERE n.beerID = 'C5RJc0'
   GROUP BY n.noteID, n.userID, n.beerID, n.note
) q JOIN `user` u ON q.userID = u.userID
ORDER BY score DESC
LIMIT 50

SQLFiddle

合并多个表并使用 COALESCE 的奇怪行为

Odd behavior combining multiple tables and using COALESCE

mysql

join

coalesce

inner-join

left-join