MySQL的價格與股票比較

Question

我有一個後續的問題我原來的職位（MySQL Compare prices）

可以說我有一個包含以下幾列表1;

例A）

|item |partnumber |supplier |stock |cost 
CD  11A   West  11  10.11 
CD  11A   East  0  10.00 
USB  BBB   North  1  125.01 
USB  BBB   West  1  101.10 

現在我已經實現了什麼（由@Ali的幫助）是表1顯示了以下（這基本上顯示了最便宜的價格供​​貨商的產品）：

實施例B）

|item |partnumber |supplier |stock |cost 
CD  11A   East  0  10.00 
USB  BBB   West  1  101.10 

This is the code for EXAMPLE B that is working: 

SELECT a.name , a.partnumber , a.supplier , a.cost FROM table1 a JOIN (
SELECT name , partnumber , MIN(cost) cost 
FROM table1 
GROUP BY name , partnumber) 
b ON a.name = b.name AND a.cost = b.cost AND a.partnumber = b.partnumber 

但是：IF與最便宜的價格供​​應商的庫存是0，但另一個供應商有超過0庫存沉綿價格不是最便宜的，我怎麼能做到這一點？下面的例子中西方將採取東的地方如下：

的C）

|item |partnumber |supplier |stock |cost 
    CD  11A   West  11  10.11 
    USB  BBB   West  1  101.10 

更清晰;總是向供應商展示庫存中最便宜的產品，除非最便宜的供應商沒有庫存中的產品，但是另一個供應商在這種情況下顯示該產品。那麼，我怎樣才能達到例子C）？

非常感謝！

Answer 1

你是否嘗試過在子查詢中添加where條件？

 
SELECT a.name , a.partnumber , a.supplier , a.cost 
FROM table1 a 
JOIN (
    SELECT name , partnumber , MIN(cost) cost 
    FROM table1 
    where stock > 0 
    GROUP BY name , partnumber 
    ) b ON a.name = b.name AND a.cost = b.cost AND a.partnumber = b.partnumber 

Answer 2

試試這個：

select a.item,a.partnumber,b.supplier,a.stock,min(a.cost) from 
(select item,partnumber,supplier,stock,min(cost) cost from 
(select * from table1) as a where stock !=0 
group by item,partnumber) as a 


LEFT JOIN 

(select item,partnumber,supplier,stock,cost from 
(select * from table1) as a where stock !=0) as b 
on a.cost = b.cost 
group by a.item,a.partnumber 

結果：

CD 11A West 11 10.11 
USB BBB West 1 101.1