發現一段經典SQL，不用循環遊標，一句update程式碼實現滾動計算結存。為方便理解，結合例項測試之

--1，源資料#t1，jcshl初值為每個sid的當前庫存數量，要實現的效果：每個sid的後一結存數量為前一jcshl結存數量-chkshl出庫數量
SELECT * FROM #t1 ORDER BY sn

sn plh sid chkshl jcshl
1 S0002 20.0000 980.0000
2 S0003 10.0000 1010.0000
3 S0003 10.0000 1010.0000
4 S0003 10.0000 1010.0000
5 S0002 10.0000 980.0000
6 S0002 1.0000 980.0000
7 S0004 20.0000 720.0000
8 S0005 10.0000 530.0000
9 S0005 10.0000 530.0000
10 S0005 10.0000 530.0000
11 S0004 10.0000 720.0000
12 S0004 1.0000 720.0000

--2，按sid排序#t2，資料順序決定分組及計算順序
SELECT * INTO #t2 FROM #t1 ORDER BY sid,sn

sn plh sid chkshl jcshl
1 S0002 20.0000 980.0000
5 S0002 10.0000 980.0000
6 S0002 1.0000 980.0000
2 S0003 10.0000 1010.0000
3 S0003 10.0000 1010.0000
4 S0003 10.0000 1010.0000
7 S0004 20.0000 720.0000
11 S0004 10.0000 720.0000
12 S0004 1.0000 720.0000
8 S0005 10.0000 530.0000
9 S0005 10.0000 530.0000
10 S0005 10.0000 530.0000

--3，滾動更新jcshl結存數量，同時填入新的plh排列號
DECLARE @plh CHAR(11),@jcshl DECIMAL(18,4),@sid CHAR(11)

UPDATE #t2 SET 
    @jcshl=jcshl=CASE WHEN sid=@sid THEN @jcshl-chkshl ELSE jcshl-chkshl END,
    @plh=plh=STR(ISNULL(@plh,0))+1,
    @sid=sid=sid

SELECT * FROM #t2

sn plh sid chkshl jcshl
1 1 S0002 20.0000 960.0000
5 2 S0002 10.0000 950.0000
6 3 S0002 1.0000 949.0000
2 4 S0003 10.0000 1000.0000
3 5 S0003 10.0000 990.0000
4 6 S0003 10.0000 980.0000
7 7 S0004 20.0000 700.0000
11 8 S0004 10.0000 690.0000
12 9 S0004 1.0000 689.0000
8 10 S0005 10.0000 520.0000
9 11 S0005 10.0000 510.0000
10 12 S0005 10.0000 500.0000