Question

我想编写一个SQL查询（SQL Server），它将返回行（按给定的顺序），但只返回给定的总数。我的客户已付给我一定的金额，我想只返回那些＆lt; =到那个金额的行。

例如，如果客户付了我370美元，表中的数据是

然后我想只返回第1,2和3行

这需要高效，因为会有数千行，所以for循环不是理想的，我想。或者SQL Server是否足够高效以使用for循环优化存储过程？

提前致谢。吉姆。

Answer 1

有两种选择。

1）三角连接

 SELECT *
 FROM YourTable Y1
 WHERE (SELECT SUM(amount) 
        FROM YourTable Y2
        WHERE Y1.id >= Y2.id ) <= 370

2）递归CTE

WITH    RecursiveCTE
AS      (
        SELECT TOP 1 id, amount, CAST(amount AS BIGINT) AS Total
        FROM YourTable
        ORDER BY id
        UNION   ALL
        SELECT  R.id, R.amount, R.Total
        FROM    (
                SELECT  T.*,
                        T.amount + Total AS Total,
                        rn = ROW_NUMBER() OVER (ORDER BY T.id)
                FROM    YourTable T
                JOIN    RecursiveCTE R
                        ON  R.id < T.id
                ) R
        WHERE   R.rn = 1 AND Total <= 370
        )
SELECT  id, amount, Total
FROM    RecursiveCTE
OPTION  (MAXRECURSION 0);

第二个可能表现更好。

在SQL Server 2012中，您将能够像

这样的东西

;WITH CTE AS
(
SELECT id, 
       amount,
       SUM(amount) OVER(ORDER BY id  
                        ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) 
          AS RunningTotal
  FROM YourTable 
  )
  SELECT *
  FROM CTE
  WHERE RunningTotal <=370

虽然可能会有更有效的方法（一旦达到总数就停止扫描）

Answer 2

直接进场：

SELECT a.id, a.amount
FROM table1 a
INNER JOIN table1 b ON (b.id <=a.id)
GROUP BY a.id, a.amount
HAVING SUM(b.amount) <= 370

不幸的是，它有N ^ 2性能问题。

Answer 3

类似的东西：

select id from 
(
select t1.id, t1.amount, sum( t2.amount ) s 
from tst t1, tst t2
where t2.id <= t1.id
group by t1.id, t1.amount
) 
where s < 370

SQL存储过程添加值并在达到最大值后停止

3 个答案: