SQL server select语句用于选择另一列的重复条目的ID

Question

考虑下面的表'Table1'

main_id         main_item_id
--------        ---------
1                    101
1                    102
2                    105
2                    105
3                    105
3                    106
4                    101
4                    101
4                    102

我需要获取main_id 2和4，因为它在100万条其他记录中有重复的main_item_id

提前致谢。

Answer 1

使用group by子句检查重复

SELECT main_id, main_item_id 
FROM table
GROUP BY main_id, main_item_id 
HAVING count(*) > 1   

Answer 2

这将选择所有具有2个或更多相同main_item_id的唯一main_id：

SELECT   DISTINCT T.main_id
FROM     YourTable T
GROUP BY T.main_id
,        T.Main_item_id
HAVING   COUNT(1) > 1