如何将相同主键的项目数据加在一起

Question

这是我的sql查询

SELECT product.productNum, product.description, prod_location.quantityOnHand 
FROM product 
INNER JOIN prod_location ON prod_location.productNum = product.productNum

这是输出。

productNum | description | quantityOnHand
660        | Reflex Paper| 100
660        | Reflex Paper| 95
660        | Reflex Paper| 64
661        | Window Clean| 200
661        | Window Clean| 67
661        | Window Clean| 38
662        | Acid        | 300
662        | Acid        | 100
662        | Acid        | 100
663        | Pens        | 400
663        | Pens        | 200
663        | Pens        | 153
664        | Door Mats   | 200

我如何获得它，以便将每个productNum的quantityOnHand相加在一起，而不是它们是Reflex Paper的3行，它只是说

productNum | description | quantityOnHand
660        | Reflex Paper| 259
661        | Window Clean| 305
662        | Acid        | 500
663        | Pens        | 753
664        | Door Mats   | 200

任何帮助都是非常感谢的。

Answer 1

像这样的东西

SELECT product.productNum, product.description, SUM(prod_location.quantityOnHand) as quantityOnHand
FROM product 
INNER JOIN prod_location ON prod_location.productNum = product.productNum
GROUP BY product.productNum

Answer 2

如果product表和prod_locatoin表之间是一对多关系。而且prduct.productNum是独一无二的

SELECT product.productNum, product.description, SUM(prod_location.quantityOnHand) as quantityOnHand
FROM product 
INNER JOIN prod_location ON prod_location.productNum = product.productNum
GROUP BY product.productNum