Question

我试图从两个表中减去两个float值：

第一个是：

select sum (cost) as "total cost" from (SELECT * 
FROM PRODUCT 
LEFT JOIN sell_bill ON sell_bill.PRODUCT_ID=PRODUCT.ID
WHERE (product.cost > sell_bill.PRICE)

它返回240。

第二个是：

select sum (price) as "total price" from (SELECT *
FROM PRODUCT 
LEFT JOIN sell_bill ON sell_bill.PRODUCT_ID=PRODUCT.ID
WHERE (product.cost > sell_bill.PRICE)

它返回140。

这就是我尝试过的：

select sum (cost) as "total cost" from (SELECT * 
FROM PRODUCT 
LEFT JOIN sell_bill ON sell_bill.PRODUCT_ID=PRODUCT.ID
WHERE (product.cost > sell_bill.PRICE)
minus 
select sum (price) as "total price" from (SELECT *
FROM PRODUCT 
LEFT JOIN sell_bill ON sell_bill.PRODUCT_ID=PRODUCT.ID
WHERE (product.cost > sell_bill.PRICE)
;

但是它返回了240 ...怎么了？

Answer 1

MINUS运算符没有达到您的期望：它不减去值，而是对数据集进行操作（返回第一个SELECT语句中所有第二行未返回的行）。

此外，您不需要使用子查询来计算SUM，例如：SELECT SUM(cost) from (SELECT...）；我删除了。

我想你只是想要：

SELECT 
    SUM(cost) - SUM(price)
FROM 
    product 
    LEFT JOIN sell_bill ON sell_bill.product_id = product.id
WHERE product.cost > sell_bill.price

Answer 2

您可以在下面尝试-

SELECT sum (cost)-sum (price) as difference
FROM PRODUCT 
LEFT JOIN sell_bill ON sell_bill.PRODUCT_ID=PRODUCT.ID
WHERE product.cost > sell_bill.PRICE

SQL Oracle中的减号查询

2 个答案: