SQL存储过程添加值并在达到最大值后停止

Question

I would like to write a SQL query (SQL Server) that will return rows (in a given order) but only up to a given total. My client has paid me a given amount, and I want to return only those rows that are <= to that amount.

For example, if the client paid me $370, and the data in the table is

 id amount
 1  100
 2  122
 3  134
 4  23
 5  200

then I would like to return only rows 1, 2 and 3

This needs to be efficient, since there will be thousands of rows, so a for loop would not be ideal, I guess. Or is SQL Server efficient enough to optimise a stored proc with for loops?

Thanks in advance. Jim.

Answer 1

A couple of options are.

1) Triangular Join

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

2) Recursive 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);  

The 2nd one will likely perform better.

In SQL Server 2012 you will be able to so something like

;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

Though there will probably be a more efficient way (to stop the scan as soon as the total is reached)

Answer 2

Straight-forward approach :

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

Unfortunately, it has N^2 performance issue.

Answer 3

something like this:

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