我有一个费用表,其中包含基于商品定价的价格截止列表中的费用。例如,第一个费用范围适用于价格为 0 美元的商品,下一层的费用为 1 美元。价格为 25 美元到下一层的商品将收取 2 美元的费用,依此类推。这是费用表:
费用
Cutoff Fee
------ ---
0 1
25 2
100 3
这是带有价格的商品表:
项目
Id Price
------ ------
1 32
2 18
3 2
4 100
结果应该是这样的:
所需的项目费用结果
Id Price Fee Total Price with fee
----- ------- ------- -----------
1 32 2 34
2 18 1 19
3 2 1 3
4 100 3 103
创建结果具有挑战性。下面是两个表之间连接结果的笛卡尔积:
Id Price Cutoff Fee
--- ------- ------- ---
1 32 0 1 -- eliminate because price is above the next cut 25
2 18 0 1
3 2 0 1
4 100 0 1 -- eliminate because price is above the next cut 25
1 32 25 2
2 18 25 2 -- eliminate because price is below this cut
3 2 25 2 -- eliminate because price is below this cut
4 100 25 2 -- eliminate because price is above (equal to) the next cut 100
1 32 100 3 -- eliminate because price is below this cut
2 18 100 3 -- eliminate because price is below this cut
3 2 100 3 -- eliminate because price is below this cut
4 100 100 3
第一个where很简单:
where price >= cut
这将列表缩小到:
Id Price Cutoff Fee
--- ------- ------- ---
1 32 0 1 -- eliminate because price is above the next cut 25
2 18 0 1
3 2 0 1
4 100 0 1 -- eliminate because price is above the next cut 25
1 32 25 2
4 100 25 2 -- eliminate because price is above (equal to) the next cut 100
4 100 100 3
问题来了:我如何过滤掉下一个定价层中的记录?这是我目前拥有的 sql。
select price, cutoff, fee from item, fee
where price >= cutoff;
我试过一个子查询:
select price, cutoff, fee,
(select min(cutoff), fee from fee where cutoff > price) as nextfee
from item, fee
where price >= cutoff;
但这给出了错误:
Operand should contain 1 Column(s)
最佳答案
解决此问题的一种方法是使用相关子查询来获取 fee
表中截止值大于或等于价格的第一笔费用:
select id, price, fee, (price + fee) as totalprice
from (select id, price,
(select fee
from fee
where price >= cutoff
order by cutoff desc
limit 1
) as fee
from item
) i
关于mysql - 如何连接或子查询表示层的表,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/20587928/