Question

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

这将返回每个外部ID的多个匹配项。然而，我正在寻找的是总结结果。

结果将是：

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

Answer 1

好的，明白了。问题的标题比问题本身更好地表达了它：）

您需要先了解每个FK出现的次数：

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

一旦你有这个，你必须将它们分组以获得每个项目出现的次数与上面相同。这将导致：

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

在行动here

中查看

Answer 2

按组计算群组返回的群组数量：

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

http://sqlfiddle.com/#!2/35661/42

如何计算一组返回的组数？

2 个答案: