sql更新排序ID语句，解答

表结构如下:

id, id1, cid
1 null 3
2 null 3
3 null 3
4 null 4 
5 null 8
6 null 8
7 null 6 
8 null 6 

现把cid=3的条件下，id1字段值更新为1,2,3递增的数值
，其也cid不等于3的ID1的值不变.

sql语句怎么写，急，道谢!

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update tb set id1=id from tb where cid='3'
试试！！

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declare @i int
set @I = 0 
update id1= @i,@i = @I +1
where cid = 3

---

SQL code:
--> 生成测试数据表:tb

IF NOT OBJECT_ID('[tb]') IS NULL
DROP TABLE [tb]
GO
CREATE TABLE [tb]([id] INT,[id1] NVARCHAR(10),[cid] INT)
INSERT [tb]
SELECT 1,NULL,3 UNION ALL
SELECT 2,NULL,3 UNION ALL
SELECT 3,NULL,3 UNION ALL
SELECT 4,NULL,4 UNION ALL
SELECT 5,NULL,8 UNION ALL
SELECT 6,NULL,3 UNION ALL
SELECT 7,NULL,3 UNION ALL
SELECT 8,NULL,6
GO
--SELECT * from [tb]

-->SQL查询如下:
update A set
a.id1=(select COUNT(1) from tb where cid=3 and id<=a.id)
from tb a
where cid=3


select * from tb
/*
id id1 cid
----------- ---------- -----------
1 1 3
2 2 3
3 3 3
4 NULL 4
5 NULL 8
6 4 3
7 5 3
8 NULL 6

(8 行受影响)
*/

{{--