整理最近新学到的几种sql写法（一）动态“循环”更新表内数据

动态“循环”更新表内数据，即此行某列的值与上一行的结果有关

1
2 CREATE TABLE t1
3 (
4 id INT IDENTITY,
5 a INT,
6 b INT,
7 c INT,
8 d INT,
9 e INT
10 )
11
12 INSERT INTO [t1] (
13 [a],
14 [b],
15 [c],
16 [d],
17 [e]
18 )
19 SELECT 1, 2, 3, 4, 0
20 UNION
21 SELECT 2, 3, 4, 5, 0
22 UNION
23 SELECT 3, 4, 5, 6, 0
24 UNION
25 SELECT 4, 5, 6, 7, 0
26
27
28
29 SELECT *
30 FROM [t1]
31
32 DECLARE @e INT
33 UPDATE [t1]
34 SET @e = ((ISNULL(@e, 0)+[c])*[d])/(a+[b]), e=@e
35
36