declare @t table
(ID int,a varchar(20),b varchar(20))insert @tselect 1,'aaa','dsd' union all
select 2,'aaa','dsada' union all
select 3,'aaa','fdfdsfs' union all
select 4,'bb','wqeqwe' union all
select 5,'hhh','ewqed' union all
select 6,'hhh','ewqe' union all
select 7,'uu','ewqe'select * from @t a
where not exists (select * from @t b where a.a=b.a and a.id>b.id)ID a b
----------- -------------------- --------------------
1 aaa dsd
4 bb wqeqwe
5 hhh ewqed
7 uu ewqe(所影响的行数为 4 行)
(ID int,a varchar(20),b varchar(20))insert @tselect 1,'aaa','dsd' union all
select 2,'aaa','dsada' union all
select 3,'aaa','fdfdsfs' union all
select 4,'bb','wqeqwe' union all
select 5,'hhh','ewqed' union all
select 6,'hhh','ewqe' union all
select 7,'uu','ewqe'select * from @t a
where not exists (select * from @t b where a.a=b.a and a.id>b.id)ID a b
----------- -------------------- --------------------
1 aaa dsd
4 bb wqeqwe
5 hhh ewqed
7 uu ewqe(所影响的行数为 4 行)
(ID int,a varchar(20),b varchar(20))insert @tselect 1,'aaa','dsd' union all
select 2,'aaa','dsada' union all
select 3,'aaa','fdfdsfs' union all
select 4,'bb','wqeqwe' union all
select 5,'hhh','ewqed' union all
select 6,'hhh','ewqe' union all
select 7,'uu','ewqe'select * from @t where id in(select min(id) from @t group by a)