組查詢和前n條記錄SQL

Question

如果我有一個表pid, sid列為pid, sid作為主鍵，並且具有price和color 。

如何創建一個SQL查詢，該查詢可以獲取color等於green的每個pid （產品ID）的最便宜價格？

例如我有行：

(1, 1, 10, "green")
(1, 2, 8, "green")
(1, 3, 11, "green")
(2, 1, 7, "green")
(2, 2, 15, "green")
(2, 3, 22, "green")
(3, 1, 10, "red")
(1, 2, 8, "red")
(1, 3, 11, "red")

然后我將收到： (1, 2, 8)->pid=1和(2, 1, 7)->pid=2 。 沒有pid=3因為它的顏色是紅色。

提前致謝。

Answer 1

SELECT pid, min(Price)
from table
Where Color='green'
group by pid

或者，如果您希望整行（並且您的sql平台支持排名）...

select * 
from
(
 select *, ROW_NUMBER() over (partition by pid order by price) rn
 from #t
 where color='green'
) v
where rn=1

Answer 2

嘗試這個，

SELECT  a.*
FROM    tableName a
            INNER JOIN
            (
                SELECT pid, min(price) minPrice
                FROM    tableName b
            ) c ON a.pid = c.pid AND
                    a.price = c.minprice
WHERE   a.color = 'green'