DECLARE @i INT,@A VARCHAR(10)
SET @i=100

UPDATE tableName
SET B=CASE WHEN A=@A THEN A+RIGHT(@i+1,2) ELSE A+'01' END,@i=CASE WHEN  A=@A  THEN @i+1 ELSE 1 END,@A=A

------解决方案--------------------
SQL code

go
if OBJECT_ID('tbl')is not null
drop table tbl
go
create table tbl(
[Message] int,
ServiceRequestId int
)
go
insert tbl
select 3905,170757 union all
select 3905,173116 union all
select 4221,173123 union all
select 4221,173127 union all
select 4221,173132

-- 查询处理

--随便选取了你的结果中的两条数据：
/*
Message    ServiceRequestId
3905    170757,173116
4221    173123,173127,173132
*/

--> 测试数据：[tblA]
if object_id('[tbl]') is not null drop table [tbl]
create table [tbl](A varchar(4),B VARCHAR(10))
insert [tbl]
select '0001',null union all
select '0001',null union all
select '0001',null union all
select '0001',null union all
select '0002',null union all
select '0002',null union all
select '0002',null union all
select '0003',null union all
select '0003',null

;with t
as(
select ROW_NUMBER()over(PARTITION by A order by getdate()) as id,
* from tbl
)
UPDATE tbl
SET B=T.A+RIGHT('00'+LTRIM(ID),2) FROM T WHERE T.A=tbl.A