如何从表中进行选择，并将值与PostgreSQL中另一个查询的结果进行分割？

假设我有这个表：

create table currency(
currency            char(3)                 
                    PRIMARY KEY,

rate                decimal,                

buy                 decimal,                 

sell                decimal                 


);

我有以下数据：

insert into currency(currency,rate,buy,sell) values('EUR', 1, 1, 1);
insert into currency(currency,rate,buy,sell) values('USD',  0.8979, 0.901, 0.887);
insert into currency(currency,rate,buy,sell) values('GBP', 1.12404, 1.14405, 1.10543);

现在我想选择基于美元汇率的汇率，然后我想所有行的汇率、买入和卖出列除以美元汇率。i、 e

我想要像这样的东西

select currency, rate/<usd exchange rate>, buy/<usd exchange rate>, sell/<usd exchange rate>  from currency;

---

您可以在一次查询中从表中提取两次：

SELECT c.currency, c.rate / u.rate AS rate, c.buy / u.rate AS buy, c.sell / u.rate AS sell 
FROM currency c, currency u 
WHERE u.currency='USD';

---

将在整个表和美元行之间执行交叉联接。

什么是

u\u money

？..@VaoTsun抱歉修复了它。。。或使用联接语法：

SELECT。。。从货币c加入货币u，货币u=美元

但是Postgres会为两者显示相同的查询计划

SELECT c.currency, c.rate / u.rate AS rate, c.buy / u.rate AS buy, c.sell / u.rate AS sell 
FROM currency c, currency u 
WHERE u.currency='USD';