表a:t1 t2 t3
a m 45
b m 67
c m 89
d n 34
e h 90
b n 98如何得到表b:
t1 t2 t3
a m 45
b m 67
c m 89
d n 34
b n 98又如何得到表c:
t1 t2 t3
b m 67
d n 34
b n 98
a m 45
b m 67
c m 89
d n 34
e h 90
b n 98如何得到表b:
t1 t2 t3
a m 45
b m 67
c m 89
d n 34
b n 98又如何得到表c:
t1 t2 t3
b m 67
d n 34
b n 98
select t1 , t2 , t3 from
(
select distinct * from a
union all
select distinct * from b
) t
group by t1,t2,t3
having count(*) = 2
from tb
where t2 not in (select t2 from tb group by t2 having count(*)>1)