如何选择重复的行（与不同的行相反）？

Question

我的表中有一个名为application_id的列，它包含像

这样的值

32,
65,
75,
75,
32,
45,
56,
78,
64

我只想获得重复的值

喜欢75,32

我认为它有点与众不同。我不知道怎么办？

Answer 1

如果您只想选择application_id，只需使用@Sayonji已建议的查询

SELECT application_id FROM MyTable GROUP BY application_id HAVING count(*) > 1

但是如果要选择所有列，则可以使用子查询来实现此目的：

SELECT DISTINCT * FROM MyTable
WHERE application_id IN
(
   SELECT application_id FROM MyTable
   GROUP BY application_id
   HAVING COUNT(*) > 1
);

或使用自我加入：

SELECT DISTINCT t1.* FROM MyTable t1
JOIN
(
   SELECT application_id FROM MyTable
   GROUP BY application_id
   HAVING COUNT(*) > 1
) t2
ON t1.application_id = t2.application_id;

请参阅this SQLFiddle

Answer 2

像

这样的东西

SELECT a_id FROM mytable GROUP BY a_id HAVING count(a_id) > 1