求sql语句 查找重复记录

Question

table表 有 a,b,c三列 想要查找a,b两列重复的记录

---

macle

Answer 1

select a,b
from table
group by a,b
having count(a+b) >1

Answer 2

如果你想要取出 a,b,c三列，可以用下面的查询

select TB.*
from [table],
 	(select a,b
	from [table]
	group by a,b
	having count(a+b) >1
	) TB_Tmp
where [table].a=TB_Tmp.a and [table].b=TB_Tmp.b

Answer 3

select * from [table] ta where (select count(1) from [table] where a=ta.a and b=ta.b)>1

Answer 4

select a,b,c from youtable ta where exits(select 1 from youtable tb where ta.a=tb.a and ta.b=tb.b and ta.c<>tb.c)