GROUP BY查詢忽略ORDER BY子句

Question

SELECT 
    deal_woot.*, 
    site.woot_off, 
    site.name AS site_name 
FROM deal_woot 
INNER JOIN site ON site.id = site_id 
WHERE site_id IN (2, 3, 4, 5, 6) 
GROUP BY site_id 
ORDER BY deal_woot.id DESC 
LIMIT 5 

我想在分組之前進行ORDER BY，我該如何做到這一點？

Answer 1

 
SELECT 
    deal_woot.*, 
    site.woot_off, 
    site.name AS site_name 
FROM deal_woot 
INNER JOIN site ON site.id = site_id 
WHERE site_id IN (2, 3, 4, 5, 6) 
GROUP BY deal_woot.id DESC, site_id 
LIMIT 5 

我假設deal_woot.id是唯一的，Grouping將基於site_id

Answer 2

由於您按site_id分組，因此只會返回1 deal_woot行。嘗試訂購MAX()，這將返回每個site_id的最高id。

SELECT 
    deal_woot.*, 
    site.woot_off, 
    site.name AS site_name 
FROM deal_woot 
INNER JOIN site ON site.id = site_id 
WHERE site_id IN (2, 3, 4, 5, 6) 
GROUP BY site_id 
ORDER BY MAX(deal_woot.id) DESC 
LIMIT 5 

注：既然是UB什麼deal_woot行實際上返回，試圖吐涎你查詢：

SELECT 
    deal_woot.*, 
    site.woot_off, 
    site.name AS site_name 
FROM site JOIN (
    SELECT site_id, MAX(deal_woot.id) MaxID 
    FROM deal_woot 
    WHERE site_id IN (2, 3, 4, 5, 6) 
    GROUP BY site_id 
) sg ON site.id = sg.site_id 
    JOIN deal_woot 
    ON site.id = deal_woot.site_id AND deal_woot.id = sg.MaxID 
ORDER BY sg.MaxID DESC 
LIMIT 5 

Answer 3

有了這樣一個子查詢：SELECT *,COUNT(*) FROM (SELECT * from actions order by date DESC) AS actions GROUP BY ip;

Answer 4

您正在對site_id執行GROUP BY，並且正在安排deal_woot.id上的記錄。

即使您在羣組之前執行Order By，輸出也會保持不變。

您是否有任何具體的要求去做這件事，因爲您的疑問與訂購無關。