SQL查询单表，比较表列值

Question

我有一张表（A），其中有一个列caseid和citin，  caseid可以有相同的citin， 我想要一个查询，我想要特殊的citin，其中有2个或更多的caseid
我试过了

select a.caseid from A as a 
 where citin in (select citin, caseid from A as c  where c.caseid != a.caseid )

有人可以帮忙吗？

Answer 1

select a.citin, count(a.caseid) 
from A a 
group by a.citin
having count(a.caseid) > 1

Answer 2

select  a.citin , count(a.caseid) from A a group by a.citin 
having count(a.caseid) >= 2;

Answer 3

SELECT a.citin, COUNT(DISTINCT a.caseid)
FROM A a
GROUP BY a.citin
HAVING COUNT(DISTINCT a.caseid) >= 2