select A.a1, min(a2), (select min(b2) from B where B.b1 = A.a1) from A
group by a1
union
select A.a1, max(a2), (select max(b2) from B where B.b1 = A.a1) From A
group by a1
select a1, min(a2), (select min(b2) from B where b1 = A.a1) from A
group by a1
union
select a1, max(a2), (select max(b2) from B where b1 = A.a1) from A
group by a1