SQL查询单表，比较表列值

Question

我有一个表（A）它具有列caseid和citin， caseid可以具有相同的citin， 我想查询哪里我想要特定的citin有2个或更多caseid
我试图

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

有人能帮忙吗？

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

Answer 3

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