SQL按范圍分組

Question

我們有兩列First_Issue和Expiry_Issue

如果我想找出問題1的訂閱者人數，可以執行以下查詢：

select COUNT(*) from Subscriber 
where First_issue <= 1 and Expiry_issue >= 1 

現在，我想編寫一個查詢，向我顯示每個問題的訂戶數量，不確定確切的起點，贊賞任何指針。

Answer 1

如果在issues表中沒有可用的所有問題編號，則可以這樣生成它們：

WITH Issues AS (
  SELECT 1 as Number
  UNION ALL
  SELECT Number + 1 as Number
  FROM Issues WHERE Number + 1 <= (SELECT MAX(Expiry_Issue) FROM Subscriber)
)
SELECT issue.Number, COUNT(DISTINCT s.id)
FROM 
  Subscriber s INNER JOIN 
  Issues i ON i.Number BETWEEN s.First_Issue AND s.Expiry_Issue