求sql语句，求大神指教

Question

查询每个人一次成功一次失败的结果，2次失败，2次成功结果不查询

Answer 1

select t.* from haha t,haha tt
WHERE t.a=tt.a and t.b<>tt.b and
t.a in (
select haha.a from haha GROUP BY haha.a HAVING COUNT(*)=2 )