1

これは私が持っているクエリです:

SELECT  p.id, COUNT(c.id) AS comments, COUNT(a.id) AS answers
FROM posts_tbl AS p
LEFT JOIN post_reply_tbl AS c ON c.post_id = p.id AND c.type IN (1,3)
LEFT JOIN post_reply_tbl AS a ON a.post_id = p.id AND a.type = 2
GROUP BY p.id

結果として得られるはずのものは次のとおりです。

ID  Answers Comments
1   3       4
2   1       1
3   0       1

しかし、代わりに私は得ています:

ID  Answers Comments
1   12      12
2   1       1
3   0       1

LEFT JOIN の 1 つだけを使用すると、どちらの LEFT JOIN を使用しても、回答/コメントに適切な量が得られます (使用する LEFT JOIN によって異なります)。しかし、両方を使用すると、2番目の結果が得られます。

* を使用した場合のサンプル結果データ:

id  username    date                subject                     year    brand   model   type    bodywork                    text                                                    image       chassis         id  post_id answer_id   username        text    date                type    id  post_id answer_id   username        text            date                type
1   Sinan Samet 2013-02-18 20:18:19 Dit is een test onderwerp   2006    Audi    A4  TFSI 2.0    TFSI 2.0 QUATTRO - 200pk    Lorem ipsum dolor sit amet consectetur adipiscing ...   test.jpg    345215453213425 5   1       NULL        Sinan Samet     Test    2013-02-26 09:19:22 1       1   1       NULL        Jan Willem      Bla             2013-02-26 14:14:17 2
1   Sinan Samet 2013-02-18 20:18:19 Dit is een test onderwerp   2006    Audi    A4  TFSI 2.0    TFSI 2.0 QUATTRO - 200pk    Lorem ipsum dolor sit amet consectetur adipiscing ...   test.jpg    345215453213425 5   1       NULL        Sinan Samet     Test    2013-02-26 09:19:22 1       2   1       NULL        Peter           Nee toch niet   2013-02-26 15:12:26 2
1   Sinan Samet 2013-02-18 20:18:19 Dit is een test onderwerp   2006    Audi    A4  TFSI 2.0    TFSI 2.0 QUATTRO - 200pk    Lorem ipsum dolor sit amet consectetur adipiscing ...   test.jpg    345215453213425 5   1       NULL        Sinan Samet     Test    2013-02-26 09:19:22 1       3   1       NULL        Homer Simpson   Doh!            2013-02-26 14:33:18 2
1   Sinan Samet 2013-02-18 20:18:19 Dit is een test onderwerp   2006    Audi    A4  TFSI 2.0    TFSI 2.0 QUATTRO - 200pk    Lorem ipsum dolor sit amet consectetur adipiscing ...   test.jpg    345215453213425 6   1       NULL        Bart Simpson    Yo      2013-02-26 08:38:37 1       1   1       NULL        Jan Willem      Bla             2013-02-26 14:14:17 2
4

1 に答える 1

4 
select
    p.id,
    COALESCE(c.comments,0) AS comments,
    COALESCE(a.answers, 0) AS answers
from
    posts_tbl as p
    left join (
        select post_id, count(*) as comments
        from post_reply_tbl
        where type in (1,3)
        group by post_id
    ) as c on p.id = c.post_id
    left join (
        select post_id, count(*) as answers
        from post_reply_tbl
        where type = 2
        group by post_id
    ) as a on p.id = a.post_id
order by id ;
于 2013-02-26T19:14:28.847 に答える