sql - 根据计数列中的最高值为每个 ID 选择 3 个值

Question

如何根据特定列值跨多行进行选择。例如我有这样的结构

+--+----+-----+
|id|data|count|
+--+----+-----+
|1 |text|30   |
+--+----+-----+
|1 |text|1    |
+--+----+-----+
|1 |text|25   |
+--+----+-----+
|1 |text|12   |
+--+----+-----+
|1 |text|50   |
+--+----+-----+
|2 |text|5    |
+--+----+-----+
|2 |text|2    |
+--+----+-----+
|2 |text|100  |
+--+----+-----+
|2 |text|50   |
+--+----+-----+
|2 |text|1000 |
+--+----+-----+
|3 |text|2    |
+--+----+-----+
|3 |text|4    |
+--+----+-----+
|3 |text|6    |
+--+----+-----+
|3 |text|8    |
+--+----+-----+

我想从每个 ID 中选择三个——基于 count 列中最高值的“前”3 个，这样我最终会得到:

+--+----+-----+
|id|data|count|
+--+----+-----+
|1 |text|30   |
+--+----+-----+
|1 |text|25   |
+--+----+-----+
|1 |text|50   |
+--+----+-----+
|2 |text|100  |
+--+----+-----+
|2 |text|50   |
+--+----+-----+
|2 |text|1000 |
+--+----+-----+
|3 |text|4    |
+--+----+-----+
|3 |text|6    |
+--+----+-----+
|3 |text|8    |
+--+----+-----+

我基本上停留在第一个 WHERE 子句上:我不想要 count 高于特定值的行，因为这可能会返回超过 3 个结果。我可以限制 3 并按计数排序，但这只适用于一个 ID。我如何为我的表中的每个不同的 ID 执行此操作？

Answer 1

您应该能够实现 windowing function像 row_number() 获取每个 id 的前 3 名:

select id, data, "count"
from 
(
  select id, data, "count",
    row_number() over(partition by id order by "count" desc) seq
  from yourtable
) d
where seq <= 3
order by id, "count";

参见 SQL Fiddle with Demo