如何计算组返回的组的数量？ [英] How to count the number of groups returned by a group by?

问题描述

select count(*) as count from table
group by foreign_id order by count 

这会返回每个外部标识的匹配数。

This returns a number of matches for each foreign id. However what im looking for is to summarise the results.

所以结果是：

10 results grouping 1 elements
5  results grouping 2 elements
7  results grouping 7 elements

推荐答案

好的，得到了​​。问题的标题比问题本身更好：）

Ok, got it. The title of the question expainls it better than the question itself :)

您需要先知道每个FK出现的次数：

You need to first know how many times each FK appears:

select count(*) as GroupAmount from t1
group by foreign_id

一旦你有了这一点，你必须分组，得到每个项目出现的次数与上述相同的方式。这将导致：

Once you have this, you have to group them to get the amount of times each item appears the same way as above. This will result in:

select GroupAmount, count(*) GroupAmountTimes from (
  select count(foreign_id) as GroupAmount from t1
  group by foreign_id
) as SubQuery
group by GroupAmount

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