SQL Oracle中的减号查询

Posted 2021-03-26

我试图从两个表中减去两个单个float值之间的减法：

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。

所以这就是我的尝试：

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 ......出了什么问题？

答案

你可以尝试下面 -

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

另一答案

MINUS运算符没有达到预期的效果：它不会减去值，它会对数据集进行操作（返回第一个SELECT语句中未被第二个SELECT语句返回的所有行）。

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

我想你只想要：

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