返回多個結果取決於數量字段

Question

我已經記錄下表：

Product  | Colour | Quantity 
--------------------------------------- 
Product A | Blue |   1 
Product A | Red  |   2 
Product B | Green |   1 

我如何編寫一個查詢返回以下?:

Product  | Colour 
--------------------------- 
Product A | Blue 
Product A | Red 
Product A | Red 
Product B | Green 

Answer 1

WITH numbers (rn) AS 
     (
     SELECT MAX(quantity) 
     FROM product 
     UNION ALL 
     SELECT rn - 1 
     FROM numbers 
     WHERE rn > 1 
     ) 
SELECT p.* 
FROM product p 
JOIN numbers n 
ON  p.quantity >= n.rn