我有一张产品表
产品:
ProdID | ProdName
1 | shirt
2 | pants
尺寸表:
SizeID | Size
1 | small
2 | med
3 | large
订单表
OrderID | ProdID | SizeID | Qty
1 | 1 | 1 | 4
2 | 1 | 1 | 3
3 | 1 | 2 | 2
4 | 2 | 1 | 1
5 | 2 | 3 | 1
我如何得到这样的结果:
ProdName | Size | Total qty ordered (group by product and size add all quantities)
shirt | small | 7
shirt | med | 2
pants | small | 1
pants | large | 1
谢谢