alter table tablename add sid int identity(1,1)
go
delete from tablename
where sid not in(select min(sid) from tablename group by col)
go
alter table tablename drop column sid
go
delete from tablename
where sid not in(select min(sid) from tablename group by col)
go
alter table tablename drop column sid
go
truncate table tablename
go
insert into tablename select * from #t