SQL 一对多从多对多的关系

Question

我正在尝试找出只列出一对多关系的 SQL 查询

下表包含 11 条记录，我想返回两行 Field1 = 7（一对多）

表1：

Field1  Field2  
1   a   
2   a   
3   b   
4   b   
5   c   
4   d   exclude 4 and 6 as d is linked to both

6   d   
6   e   
7   f   One to Many
7   j   One to Many
8   g   

Answer 1

您希望每个field1 的所有field2 值出现一次。下面是一个使用窗口函数的方法：

select field1
from (select t.*,
             count(*) over (partition by field2) as num_field2
      from t
     ) t
group by field1
having count(*) > 1 and max(num_field2) = 1;