create table ca
(ID int, A  int, B int)

insert into ca
select 1, 10, 0 union all
select 2, 10, 0 union all
select 3, 10, 1 union all
select 4, 10, 2 union all
select 5, 11, 0 union all
select 6, 12, 3 union all
select 7, 12, 3 union all
select 8, 13, 4


select t.ID, t.A, t.B from
(select row_number() over(partition by A order by B) rn, 
* from ca) t where t.rn=1

ID          A           B
----------- ----------- -----------
1           10          0
5           11          0
6           12          3
8           13          4

------解决方案--------------------
SQL code
select * from tb t where id=(select min(id) from tb where a=t.a)

------解决方案--------------------
探讨


SQL code

create table ca
(ID int, A  int, B int)

insert into ca
select 1, 10, 0 union all
select 2, 10, 0 union all
select 3, 10, 1 union all
select 4, 10, 2 union all
select 5, 11, 0 union all
se……