Question

每条记录都包含RecordID, TypeID, GroupID Type有很多记录，Group有很多类型的记录我想为每种类型和组合返回3条记录。

有什么建议吗？

这样的简化输出

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..

这是对我有用的解决方案，是给出答案的一种变体。

它是迁移的代码，因此绝对优化不是必需的 - 但需要进一步了解。

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

尝试这样的事情：

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

为每个组变体选择有限数量的记录

1 个答案: