go
if OBJECT_ID('test')is not null
drop table test
go
create table test(
A char(5),
B char(2),
C int
)
go
insert test
select 'b1101','b1',101

--按照你的要求建立触发器
go
if OBJECT_ID('tri_tracy')is not null
drop trigger tri_tracy
go
create trigger tri_tracy on test
instead of insert
as
declare @A char(5),@B char(2),@C int
select @B=B from inserted
select @A=@B+ltrim(max(C)+1),@C=max(C)+1 from test
insert test values(@A,@B,@C)

go
insert test(B)
select 'B2'

select * from test
/*
A    B    C
b1101    b1    101
B2102    B2    102
*/