Question

我需要根据列qty

的总和来限制查询结果

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

因此我需要得到：

| id | qty | wh | car |
-----------------------
| x3 | 10  | a  | z   |
| x4 | 5   | a  | z   |
| x7 | 3   | a  | z   |
| x1 | 2   | a  | z   |

我想我可能需要使用子查询？

Answer 1

您可以尝试此查询，首先将一个数字作为ID rn，然后累加两个数据集，判断大于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：http://sqlfiddle.com/#!9/22740/6

基于sum（）的SQL查询限制

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