为每组变体选择有限的记录数

Question

每个记录包含RecordID, TypeID, GroupID。
有许多记录到Type和许多类型到Group。
我想为类型和组的每个组合返回3条记录。

有什么建议吗？

这样

Group | Type | Record 
------+------+-------- 
1  | 1 | 1 
1  | 1 | 2 
1  | 1 | 3 
1  | 2 | 1 
1  | 2 | 2 
1  | 2 | 3 
1  | 3 | 1 
.... 
9  | 1 | 1 
9  | 2 | 2 
etc.. 

这种简化的输出是为我工作，给出的答案的变化的解决方案。

它是代码迁移，所以绝对优化是不必要的 - 但要欣赏更多的指针。

SELECT * 
FROM yourTable t1 
WHERE EXISTS 
    (SELECT RecordId 
    FROM (
     SELECT RecordId, ROW_NUMBER() OVER (PARTITION BY GroupId, TypeId ORDER BY RecordId) As seq FROM yourTable) t2 
     WHERE seq <= 3 AND t2.RecordId = t1.RecordId 
    ) 
ORDER BY GroupId, TypeId 

Answer 1

尝试这样：

SELECT * 
FROM (
    SELECT *, ROW_NUMBER() OVER (PARTITION BY GroupId, TypeId ORDER BY RecordId) As seq 
    FROM yourTable) dt 
WHERE seq <= 3