COST

Question

假设我有下面的表格，里面有几百种不同颜色的玩具...

---------------------------
  ITEM  |  COST  |  COLOR
---------------------------
    1   |  12.00 |  BLUE
    2   |  10.98 |  RED
    3   |   9.34 |  BLUE
    4   |  11.33 |  WHITE
    5   |   8.00 |  YELLOW
    .   |    .   |    .
    .   |    .   |    .
    .   |    .   |    .

如果我想选择三个价格最低的蓝色玩具，我当然可以写...。

SELECT * FROM TOYS WHERE Color = 'BLUE' ORDER BY COST LIMIT 3;

但是，有没有一种方法可以让我选择唯一指定数量的价格最低的黄色、白色和蓝色玩具，就像我说...

 SELECT * FROM TOYS WHERE COLOR = 'YELLOW' (LIMIT 1) AND COLOR = 'WHITE' (LIMIT 3) AND COLOR = 'BLUE' (LIMIT 2) ORDER BY COST

是否可以在MySQL中完全做到这一点，而不用在PHP中走过数组？

Answer 1

select * from toys where color = 'Yellow' (LIMIT 1)
UNION
select * from toys where color = 'White' (LIMIT 3)
UNION
select * from toys where color = 'Blue' (LIMIT 2)

Answer 2

Answer 3

(select * from toys where color = 'Yellow' LIMIT 1)
UNION ALL
(select * from toys where color = 'White' LIMIT 1)

Answer 4

可以使用。

SELECT *
FROM (SELECT *, ROW_NUMBER() OVER(PARTITION BY COLOR ORDER BY COST) AS RN
      FROM TOYS
      WHERE COLOR IN ('YELLOW', 'WHITE', 'BLUE')) sub
WHERE RN <= CASE COLOR WHEN 'YELLOW' THEN 1 WHEN 'WHITE' THEN 3 WHEN 'BLUE' THEN 2 END  

Answer 5