この問題を解決する 1 つの方法は、クエリ全体をサブクエリでラップすることです。
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
ちなみに、彼らは呼ばれていALIAS
ます。
ALIAS
定義された同じレベルでの計算に使用できない理由は、サーバーが句のFROM
前にSELECT
句を実行するためです。これらALIAS
はSELECT
節にあります。完全な SQL の操作順序は次のとおりです。
- FROM 句
- WHERE句
- GROUP BY 句
- HAVING 句
- SELECT句
- ORDER BY 句
より良いパフォーマンスの問題のために、私はJOIN
むしろ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