Question

这是我的代码： 'media_work'表有一个'order'字段，表示文件的顺序。我想对'media_work'表的结果进行排序以获得第一项（图像）

此代码有效，但未订购'media_work'

SELECT work.id, work.title, media.file_name_thumb,media_work.order, 
COUNT(media.file_name_thumb) AS mycount
FROM work
LEFT OUTER JOIN media_work ON media_work.work_id = work.id
LEFT OUTER JOIN media ON media_work.media_id = media.id
GROUP BY work.id ORDER BY work.id DESC

这是结果

id   title          file_name_thumb                 order   mycount
-------------------------------------------------------------------
3    laatste        thumb_20101028134738_278.gif    1       3
2    test work add  thumb_20101028133811_893.gif    1       56
1    test werk      thumb_20101028132316_537.jpg    2       5

我希望订单按顺序升序，因此它将为'0'

Answer 1

如果您想为每个media选择第一个work：

SELECT  work.id, work.title, media.file_name_thumb,
        (
        SELECT  COUNT(*)
        FROM    media_work
        WHERE   media_work.work_id = work.id
        )
FROM    work
LEFT JOIN
        media
ON      media.id =
        (
        SELECT  media_work.media_id
        FROM    media_work
        WHERE   media_work.work_id = work.id
        ORDER BY
                media_work.work_id, media_work.order
        LIMIT 1
        )

在media_work (work_id, order)上创建一个索引，以便快速工作。

订购左连接的结果

1 个答案: