select
case when a.a1<>3 then b.b2
when b.b2 is null then b.b22 end 条件1,
case when a.a1<>3 then b.b3
when b.b3 is null then b.b33 end 条件2,
case when a.a1<>3 then b.b4
when b.b4 is null then b.b44 end 条件3,
case when a.a1<>3 then b.b5
when b.b5 is null then b.b55 end 条件4
from A join B on a.a0=b.b0这样不知是不是楼主要的
case when a.a1<>3 then b.b2
when b.b2 is null then b.b22 end 条件1,
case when a.a1<>3 then b.b3
when b.b3 is null then b.b33 end 条件2,
case when a.a1<>3 then b.b4
when b.b4 is null then b.b44 end 条件3,
case when a.a1<>3 then b.b5
when b.b5 is null then b.b55 end 条件4
from A join B on a.a0=b.b0这样不知是不是楼主要的
union all
select ... from a , b where 条件2
union all
select ... from a , b where 条件3
union all
select ... from a , b where 条件4