GROUP BY查询忽略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 

我想在分组之前进行ORDER BY，我该如何做到这一点？

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 

我假设deal_woot.id是唯一的，Grouping将基于site_id

Answer 2

由于您按site_id分组，因此只会返回1 deal_woot行。尝试订购MAX()，这将返回每个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什么deal_woot行实际上返回，试图吐涎你查询：

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

有了这样一个子查询：SELECT *,COUNT(*) FROM (SELECT * from actions order by date DESC) AS actions GROUP BY ip;

Answer 4

您正在对site_id执行GROUP BY，并且正在安排deal_woot.id上的记录。

即使您在群组之前执行Order By，输出也会保持不变。

您是否有任何具体的要求去做这件事，因为您的疑问与订购无关。