How to delete duplicate rows in SQL Server 2008

Imagine that you have a table like:

create table T (
    id int identity,
    colA varchar(30) not null,
    colB varchar(30) not null
)

Then you can say something like:

delete T
from T t1
where exists
(select null from T t2
where t2.colA = t1.colA
and t2.colB = t1.colB
and t2.id <> t1.id)

Another trick is to select out the distinct records with the minimum id, and keep those:

delete T
where id not in
(select min(id) from T
group by colA, colB)