如何使用PostgreSQL中以前定义的列进行计算？

我正在尝试使用先前声明的列来计算列。我认为这将在MySQL中起作用，但我不确定PostgreSQL中该如何做。如何使用PostgreSQL中以前定义的列进行计算？

我的声明是这样的：

SELECT customerNumber, customerName, (
    SELECT COALESCE(SUM(payments.amount), 0) 
    FROM payments 
    WHERE customers.customerNumber = payments.customerNumber 
) as totalOfPaymentsMade,(
    SELECT COALESCE(SUM(orderdetails.priceeach * orderdetails.quantityordered), 0) 
    FROM orders 
    LEFT JOIN orderdetails ON orderdetails.ordernumber = orders.ordernumber 
    WHERE customers.customerNumber = orders.customerNumber 
) as totalValueOfAllOrdersMade, creditLimit, creditLimit + totalOfPaymentsMade - totalValueOfAllOrdersMade as amountOfAvailableCredit 
FROM customers 
ORDER BY customerNumber

我收到此错误信息：column "totalofpaymentsmade" does not exist LINE 11: ...lValueOfAllOrdersMade, creditLimit, creditLimit + totalOfPay...

来源

2014-09-30 Sebastian

不要你错过了GROUP BY中的款项报表？ – CapelliC 2014-09-30 16:27:23

我想我现在不需要GROUP BY语句，因为我使用的是subquerys，并且希望SUM匹配我的WHERE子句的所有行。 – Sebastian 2014-09-30 16:36:31

试试这个：

SELECT 
    *, 
    creditLimit + totalOfPaymentsMade - totalValueOfAllOrdersMade 
    as amountOfAvailableCredit 
from 
(

SELECT 
    customerNumber, 
    customerName, 
    creditLimit, 

    (
     SELECT COALESCE(SUM(payments.amount), 0) 
     FROM payments 
     WHERE customers.customerNumber = payments.customerNumber 
    ) 
    as totalOfPaymentsMade, 

    (
     SELECT COALESCE(SUM(orderdetails.priceeach * orderdetails.quantityordered), 0) 
     FROM orders 
     LEFT JOIN orderdetails ON orderdetails.ordernumber = orders.ordernumber 
     WHERE customers.customerNumber = orders.customerNumber 
    ) 
    as totalValueOfAllOrdersMade 

FROM customers 

) a 

ORDER BY customerNumber

来源

2014-09-30 17:09:38 Christian

非常感谢！为我节省了几个小时！ – Sebastian 2014-09-30 23:29:09

如何使用PostgreSQL中以前定义的列进行计算？

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