Mysql 基于sum（）的SQL查询限制

我需要根据列数量的总和限制查询结果

例如，这是我的数据库

| id | qty | wh | car |
-----------------------
| x1 | 2   | a  | z   |
| x2 | 3   | b  | y   |
| x3 | 10  | a  | z   |
| x4 | 5   | a  | z   |
| x5 | 2   | b  | z   |
| x6 | 2   | a  | z   |
| x7 | 3   | a  | z   |

这是我的疑问：

SELECT * FROM table WHERE wh = 'a' AND car = 'z' ORDER BY qty LIMIT sum(qty) <= 20

---

我想我可能需要使用子查询？

您可以尝试此查询，首先将一个数字作为ID rn，然后累积两个数据集，判断值大于20

SELECT t1.id,t1.qty,t1.wh,t1.car 
FROM (
  select t.*,(@rn:=@rn+1) rn
  from
  (
    SELECT *
    FROM T 
    WHERE wh = 'a' AND car = 'z' 
    ORDER BY qty asc
  ) t CROSS JOIN (select @rn:=0) a
)t1 CROSS JOIN
(
  select t.*,(@rn1:=@rn1+1) rn
  from
  (
    SELECT *
    FROM T 
    WHERE wh = 'a' AND car = 'z' 
    ORDER BY qty asc
  ) t CROSS JOIN (select @rn1:=0) a
)t2 
WHERE t1.rn < t2.rn + 1
group by t1.id,t1.qty
HAVING sum(t2.qty) <= 20
ORDER BY t1.qty DESC

---

sqlfiddle:

谢谢，伙计，它工作得很好！我们应该注意，以这种方式使用的用户定义变量的行为设置一个变量并在同一语句中读取它并不能保证。参考：

SELECT t1.id,t1.qty,t1.wh,t1.car 
FROM (
  select t.*,(@rn:=@rn+1) rn
  from
  (
    SELECT *
    FROM T 
    WHERE wh = 'a' AND car = 'z' 
    ORDER BY qty asc
  ) t CROSS JOIN (select @rn:=0) a
)t1 CROSS JOIN
(
  select t.*,(@rn1:=@rn1+1) rn
  from
  (
    SELECT *
    FROM T 
    WHERE wh = 'a' AND car = 'z' 
    ORDER BY qty asc
  ) t CROSS JOIN (select @rn1:=0) a
)t2 
WHERE t1.rn < t2.rn + 1
group by t1.id,t1.qty
HAVING sum(t2.qty) <= 20
ORDER BY t1.qty DESC