用sum（cloumnC）選擇不同的columnA和columnB

Question

我有一張這樣的桌子：

importer     exporter     quantity    
A            D           0.9
A            B           0.9
A            B           0.1
B            E           9.4
B            E           8.9
B            D           9.4
C            P           9.0
C            V           1.0
C            P           0.9

我想找到與sum（columnC）不同的columnA和columnB，並且表是ORDER BY SUM（columnC）DESC。

importer     exporter     quantity
B            E           18.3
C            P           9.9
B            D           9.4    
A            B           1.0
C            V           1.0
A            D           0.9

當我嘗試

 SELECT DISTINCT
 IMPORTER, EXPORTER, QUANTITY
 FROM Tablename;

表MYsql顯示的不是columnA和columnB，這實際上是重復的columnA和columnB，並且沒有將columnC加起來。

Answer 1

嘗試這個：

SELECT   importer,
         exporter,
         SUM(quantity) AS sum_quantity
FROM     tablename
GROUP BY importer,
         exporter
ORDER BY sum_quantity DESC;

Answer 2

嘗試如下

 SELECT 
 IMPORTER, EXPORTER, sum(QUANTITY)
 FROM Tablename group by IMPORTER, EXPORTER

Answer 3

正如@GordonLinoff所暗示的，您需要的是GROUP BY查詢

SELECT 
    IMPORTER, 
    EXPORTER, 
    SUM(QUANTITY)
FROM Tablename
GROUP BY
    IMPORTER, 
    EXPORTER
ORDER BY 
    SUM(QUANTITY) DESC;

Answer 4

這是基本的GROUP BY：

 SELECT 
 IMPORTER, EXPORTER, SUM(QUANTITY) AS SUMQUANTITY
 FROM Tablename
 GROUP BY IMPORTER, EXPORTER
 ORDER BY SUMQUANTITY DESC;