简单模型,向顾客卖书
有三个表,图书表book, 订单表order, 顾客表customer
我现在想看下每种书卖出去多少,查询结果表为两列,一列为书名字,一列为卖出去的总数
如果一种书一本也没卖出去,则书名字显示出来,总数显示为0
SELECT Book.bookID,SUM(orderQuantity)
FROM Order FULL JOIN Book
ON Book.bookID=Order.bookID
GROUP BY Book.bookID;
我使用了book表和order表的full join。因为这样才会把没有卖出去的书名也打印出来。但是如果一本书没卖出去,总销售量显示为null,怎样使它显示为0,以方便我后续的计算。非常感谢各位指点!!!
有三个表,图书表book, 订单表order, 顾客表customer
我现在想看下每种书卖出去多少,查询结果表为两列,一列为书名字,一列为卖出去的总数
如果一种书一本也没卖出去,则书名字显示出来,总数显示为0
SELECT Book.bookID,SUM(orderQuantity)
FROM Order FULL JOIN Book
ON Book.bookID=Order.bookID
GROUP BY Book.bookID;
我使用了book表和order表的full join。因为这样才会把没有卖出去的书名也打印出来。但是如果一本书没卖出去,总销售量显示为null,怎样使它显示为0,以方便我后续的计算。非常感谢各位指点!!!
FROM Order FULL JOIN Book
ON Book.bookID=Order.bookID
GROUP BY Book.bookID;
FROM Order FULL JOIN Book
ON Book.bookID=Order.bookID
GROUP BY Book.bookID;
FROM Order FULL JOIN Book
ON Book.bookID=Order.bookID
GROUP BY Book.bookID
(CASE WHEN SUM(orderQuantity)=NULL THEN 0 ELSE SUM(orderQuantity)) SUM(orderQuantity)没他们简单