--这是我在SQL 2005中写的SQL：
create table #tb(id int,tname nvarchar(10))
insert into #tb
    select 1,'x' union all
    select 2,'y'

begin
declare @i int
select @i =  count(1) from #tb where id=1 and tname='a'
if @i = 0
    begin
        insert into #tb values (1,'a');
        update #tb set tname='aa' where id=1 and tname='a'
    end

select @i =  count(1) from #tb where id=2 and tname='y'
if @i=0
    begin
        insert into #tb values (2,'y');
        update #tb set tname='yy' where id=1 and tname='y'
    end

select @i =  count(1) from #tb where id=1 and tname='c'
if @i = 0
    begin
        insert into #tb values (1,'c');
        update #tb set tname='cc' where id=1 and tname='c'
    end
end

select * from #tb