MySQL计算不同的查询

Question

我有一张表，我一直保留帖子comment_type，amount等。

PostExtras
- id
- amount
- post_id (foreign key)
- comment_type (foreign key)
- ...

comment_type
- id
- name

我想选择具有重复注释类型的帖子。

示例：

- id     - amount    - post_id    - comment_type
 1         20          23           1
 2         45          23           2
 3         80          28           1
 4         78          28           2
 5         56          23           1

第1行和第5行实际上是相同的。

Answer 1

如果我理解正确，请使用COUNT, GROUP BY and HAVING

SELECT *, COUNT(*) AS itemcount FROM PostExtras 
GROUP BY post_id, comment_type
HAVING itemcount >= 2

Answer 2

SELECT post_id FROM PostExtras
GROUP BY post_id, comment_type
HAVING COUNT(comment_type) > 1