如何將行隨機與MySQL轉換爲列

如何將行隨機與MySQL轉換爲列？鮮明（IMAGE_URL）如何將行隨機與MySQL轉換爲列

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()

而且，在此查詢

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

如何顯示null如果小於4 IMAGE_URL和如何使它不同？

來源

2012-09-10 user1615767

是否要顯示錶中的一個電子郵件地址和四個隨機選擇的圖像？ –

是的。任何想法？怎麼做？ – user1615767

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

來源

2012-09-10 09:51:41

昂貴;最終可能會有相同的圖像多次;並且不應該在'p.email'上的每個子查詢過濾器？ – eggyal

也許它很昂貴，但我不認爲這樣的查詢是擺在超過幾千行的表上。是的，電子郵件過濾器應該/可以添加。但只要我們不知道什麼是OP針對... –

選擇電子郵件，（選擇IFNULL（（從民調P1 ORDER BY蘭特IMAGE_URL（）限制1），NULL）作爲IMAGE_1，（選擇IMAGE_URL從輪詢p2 order by rand（）limit 1）as image_2，（從輪詢p3中選擇image_url by rand（）limit 1）as image_3，（從輪詢p4中選擇image_url by rand（）limit 1）as image_4 來自投票通過電子郵件分組我如何顯示NULL，如果有少於4 image_url？ – user1615767

如何將行隨機與MySQL轉換爲列

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