Question

我有以下mySQL查询，我想给出在具有相应行位置的计算字段上排序的行。我已经使用来自here的OMG Ponies代码作为模板，但是行返回的编号错误（它们按密钥（gemid）顺序编号，没有排序）。我知道它与GROUP BY上的JOIN有关，但我知道如何修复它。提前谢谢。

SELECT g.gemid, sum_rating, @rownum := @rownum + 1 AS row_num FROM gems g
    LEFT JOIN (SELECT gemid, SUM(rating) as sum_rating from gemrating GROUP BY gemid) rt ON g.gemid = rt.gemid 
    JOIN (SELECT @rownum := 0) Z 
    WHERE g.grade = '8'  
    ORDER BY sum_rating asc

输出应该看起来像：

gemid    sum_rating    row_num
------   ------------  ----------
2           10           1
4           25           2
1           40           3
3           41           4

相反它会回来：

gemid    sum_rating    row_num
------   ------------  ----------
2           10           2
4           25           4
1           40           1
3           41           3

Answer 1

看起来这样有效。我知道在编号之前我必须先对记录进行排序，然后从有序列表中选择SELECT。

SELECT g2.gemid, g2.sum_rating, @rownum := @rownum + 1 AS row_num FROM 

(SELECT g.gemid, rt.sum_rating, g.grade FROM gems g
    LEFT JOIN (SELECT gemid, SUM(rating) as sum_rating from gemrating GROUP BY gemid) rt ON g.gemid = rt.gemid 
 WHERE g.grade = '8'  ) g2

    JOIN (SELECT @rownum := 0) Z 
    WHERE g2.grade = '8'  
    ORDER BY sum_rating asc

MySQL获取行位置，ORDER BY编号错误

1 个答案: