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mysqlで行をランダムに列に変換する方法は? 個別 (image_url)

 select p.email , 
        image_url AS image_url_1,
        image_url AS image_url_2 ,
        image_url  AS image_url_3,
        image_url  AS image_url_4
    FROM
        poll p
    GROUP BY
        email
    ORDER by RAND()

また、このクエリでは

select email,
    (select IFNULL((image_url from poll p1 order by rand() limit 1), NULL) as image_1,
    (select IFNULL((image_url from poll p2 order by rand() limit 1), NULL) as image_2,
    (select IFNULL((image_url from poll p3 order by rand() limit 1), NULL) as image_3,
    (select IFNULL((image_url from poll p4 order by rand() limit 1), NULL) as image_4
from poll
group by email

nullimage_urlが4つ未満の場合の表示方法と区別する方法は?

4

1 に答える 1

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select email,
(select image_url from poll p1 order by rand() limit 1) as image_1,
(select image_url from poll p2 order by rand() limit 1) as image_2,
(select image_url from poll p3 order by rand() limit 1) as image_3,
(select image_url from poll p4 order by rand() limit 1) as image_4
from poll
于 2012-09-10T09:51:41.417 に答える