如何在 MySQL SUM 子查询中创建可用的别名

Question

在下面的 MySQL 查询中，我能够生成一个 Sum 值，但无法分配可用于在 PHP 页面中回显的值。

SELECT
    invoices.InvoiceNo AS Invoice,
    invoices.invDate AS DATE,
    invoices.invValue AS Amount,
    (
        SELECT SUM(invoices.invValue) AS GrandTotal
        FROM invoices
        WHERE invoices.fKey = 186 AND inv_openClosed = 0
    )
FROM invoices
WHERE invoices.fKey = 186 AND inv_openClosed = 0
ORDER BY Invoice DESC

测试显示结果，但 "GrandTotal" 的别名不起作用。并且MySQL没有错误去寻求解决方案。

查询结果如下：

Answer 1

与其在子查询中使用别名，不如为其结果设置别名：

SELECT
    invoices.InvoiceNo AS Invoice,
    invoices.invDate AS DATE,
    invoices.invValue AS Amount,
    (
        SELECT SUM(invoices.invValue) 
        FROM invoices
        WHERE invoices.fKey = 186 AND inv_openClosed = 0
    ) AS GrandTotal
FROM invoices
WHERE invoices.fKey = 186 AND inv_openClosed = 0
ORDER BY Invoice DESC

Answer 2

别名需要在外部查询中而不是内部查询:

SELECT i.InvoiceNo AS Invoice,
       i.invDate AS DATE,
       i.invValue AS Amount,
       (SELECT SUM(i2.invValue)
        FROM invoices i2
        WHERE i2.fKey = 186 AND i2.inv_openClosed = 0
       )  AS GrandTotal
FROM invoices i
WHERE i.fKey = 186 AND i.inv_openClosed = 0
ORDER BY i.Invoice DESC;

您会注意到我还包含了 table 别名和限定的列名。你也可以把它写成一个相关的子查询，所以你不需要重复常量：

       (SELECT SUM(i2.invValue)
        FROM invoices i2
        WHERE i2.fKey = i.fKey AND i2.inv_openClosed = i.inv_openClosed
       )  AS GrandTotal

而在 MySQL 8+ 中，您可以使用 window 函数：

SELECT i.InvoiceNo AS Invoice,
       i.invDate AS DATE,
       i.invValue AS Amount,
       SUM(i.invValue) OVER (PARTITION BY fKey, inv_openClosed) as GrandTotal
FROM invoices i
WHERE i.fKey = 186 AND i.inv_openClosed = 0
ORDER BY i.Invoice DESC;

如何在 MySQL SUM 子查询中创建可用的别名

How to create usable alias in MySQL SUM subquery

mysql

sql

date

subquery

window-functions