表t有 一列 samplecode，程序每次生成id的时候都先从这里获取最大值再加1，初始值是A0000001，然后到A9999999的时候则是到B0000001 共8位

drop table x
go
create table x(id varchar(10))
--insert into x values(‘A001‘)
go
with a as (
select ISNULL(max(id),‘A0000‘) maxid from x)
insert into x (id)
select
case when RIGHT(maxid,4)<9999
THEN LEFT(maxid,1)+RIGHT(‘000‘+CAST(RIGHT(maxid,4)+1 AS VARCHAR(10)),4)
ELSE CHAR(ASCII(LEFT(maxid,1))+1)+‘0001‘
end
from a
go 10000
select * from x
go