3

在以下查询中，我总结了给定范围内所有销售的所有销售项目。此摘要中包含“sumOfCost”和“sumOfPrice”，我也想要“sumOfProfit”。问题是，由于它们只是“AS”变量，我不确定如何引用它们，而我的尝试“...... Blah AS blah, sumOfPrice - sumOfCost = sumOfProfit ...”很遗憾没有奏效！

这是我的查询：

SELECT  Sales.SaleID, 
        Sales.StaffID, 
        Sales.CustomerID, 
        Sales.Timestamp, 
        Sales.Refunded, 
        Sales.PaymentType, 
        Staff.Forename AS staffForename, 
        Staff.Surname AS staffSurname, 
        (   
            SELECT GROUP_CONCAT(Quantity, ' x ', Name) 
            FROM SaleItems 
            WHERE SaleItems.SaleID = Sales.SaleID
        ) AS itemList, 
        (
            SELECT sum(Cost*Quantity) 
            FROM SaleItems 
            WHERE SaleItems.SaleID = Sales.SaleID
        ) AS sumOfCost, 
        (
            SELECT sum(Price*Quantity) 
            FROM SaleItems 
            WHERE SaleItems.SaleID = Sales.SaleID
        ) AS sumOfPrice 
FROM    Sales 
        INNER JOIN Staff 
            ON Sales.StaffID = Staff.StaffID 
WHERE   Sales.Deleted = '0' 
ORDER   BY Timestamp DESC 
LIMIT   0, 15

为查询的长度道歉，我之前一直在努力优化它，但现在我只想解决这个问题。

提前致谢 ：）

4

1 回答 1

2

解决此问题的一种替代方法是使用子查询包装整个查询，

SELECT  *,
        sumOfCost - sumOfPrice AS sumOfProfit
FROM
    (
        SELECT  Sales.SaleID, 
                Sales.StaffID, 
                Sales.CustomerID, 
                Sales.Timestamp, 
                Sales.Refunded, 
                Sales.PaymentType, 
                Staff.Forename AS staffForename, 
                Staff.Surname AS staffSurname, 
                (   
                    SELECT GROUP_CONCAT(Quantity, ' x ', Name) 
                    FROM SaleItems 
                    WHERE SaleItems.SaleID = Sales.SaleID
                ) AS itemList, 
                (
                    SELECT sum(Cost*Quantity) 
                    FROM SaleItems 
                    WHERE SaleItems.SaleID = Sales.SaleID
                ) AS sumOfCost, 
                (
                    SELECT sum(Price*Quantity) 
                    FROM SaleItems 
                    WHERE SaleItems.SaleID = Sales.SaleID
                ) AS sumOfPrice 
        FROM    Sales 
                INNER JOIN Staff 
                    ON Sales.StaffID = Staff.StaffID 
        WHERE   Sales.Deleted = '0' 
        ORDER   BY Timestamp DESC 
        LIMIT   0, 15
    ) s

顺便说一句，它们被称为ALIAS。

ALIAS不能在定义它们的同一级别上用于计算的原因是服务器在子句FROM之前执行SELECT子句。ALIASare 在子句上，这SELECT是完整的 SQL 操作顺序：

  • FROM 子句
  • WHERE 子句
  • GROUP BY 子句
  • HAVING 子句
  • 选择子句
  • ORDER BY 子句

为了更好的性能问题，我宁愿使用JOINthan subqueries。

更新 1

SELECT  Sales.SaleID, 
        Sales.StaffID, 
        Sales.CustomerID, 
        Sales.Timestamp, 
        Sales.Refunded, 
        Sales.PaymentType, 
        Staff.Forename AS staffForename, 
        Staff.Surname AS staffSurname, 
        COALESCE(a.itemList, '') itemList,
        COALESCE(b.sumOfCost, 0) sumOfCost, 
        COALESCE(c.sumOfPrice, 0) sumOfPrice,
        COALESCE(b.sumOfCost, 0) - COALESCE(c.sumOfPrice, 0) AS sumOfProfit
FROM    Sales 
        INNER JOIN Staff 
            ON Sales.StaffID = Staff.StaffID 
        LEFT JOIN 
        (   
            SELECT SaleID, GROUP_CONCAT(Quantity, ' x ', Name) itemList
            FROM SaleItems 
            GROUP BY SaleID
        ) a ON a.SaleID = Sales.SaleID
        LEFT JOIN
        (
            SELECT SaleID, sum(Cost*Quantity) sumOfCost
            FROM SaleItems 
            GROUP BY SaleID
        ) b ON b.SaleID = Sales.SaleID
        LEFT JOIN
        (
            SELECT SaleID, sum(Price*Quantity) sumOfPrice 
            FROM SaleItems 
            GROUP BY  SaleID
        ) c ON c.SaleID = Sales.SaleID
WHERE   Sales.Deleted = '0' 
ORDER   BY Timestamp DESC 
LIMIT   0, 15

更新 2

SELECT  Sales.SaleID,
        Sales.StaffID,
        Sales.CustomerID,
        Sales.TIMESTAMP,
        Sales.Refunded,
        Sales.PaymentType,
        Staff.Forename AS staffForename,
        Staff.Surname AS staffSurname,
        COALESCE(a.itemList, '') itemList,
        COALESCE(a.sumOfCost, 0) sumOfCost,
        COALESCE(a.sumOfPrice, 0) sumOfPrice,
        COALESCE(a.sumOfCost, 0) - COALESCE(a.sumOfPrice, 0) AS sumOfProfit
FROM    Sales
        INNER JOIN Staff
            ON Sales.StaffID = Staff.StaffID
        LEFT JOIN
        (  
            SELECT      SaleID,
                        GROUP_CONCAT(Quantity, ' x ', Name) itemList,
                        SUM(Cost*Quantity) sumOfCost,
                        SUM(Price*Quantity) sumOfPrice
            FROM SaleItems
            GROUP BY SaleID
        ) a ON a.SaleID = Sales.SaleID
WHERE   Sales.Deleted = '0'
ORDER   BY TIMESTAMP DESC
LIMIT   0, 15
于 2013-01-22T11:10:50.743 回答