declare @AlyID int

select @AlyID=AlyID from tableA WHERE comid=1 --查看表是否存在数据

if isnull(@AlyID,'')!='' and @AlyID !='' --存在数据，进行修改

begin

UPDATE tableA SET columnA='' WHERE columnA =1  --修改

SELECT @AlyID as AlyID

END

ELSE

begin

insert into tableA( )values( )   --新增

select @@identity as AlyID     --得到自增ID

END