Sql server 如何使用sum函数进行分组查询

我在SQL Server中有

inventoryTransaction

表，如下所示：

productID StockLocationID TransactionType   Quantity
1046          1                "in"           100
1046          1               "out"            20
1046          2                "in"            70
1046          2               "out"            65
...

如何进行查询，输出如下：

productID  StockLocationID     stock
1046          1                 80
1046          2                 5

您可以尝试：

SELECT 
    productID, 
    StockLocationID,
    SUM(CASE 
            WHEN TransactionType = 'out' THEN -1 
            ELSE 1 
        END) * Quantity) AS stock
GROUP BY 
    productID, 
    StockLocationID

您可以尝试：

SELECT 
    productID, 
    StockLocationID,
    SUM(CASE 
            WHEN TransactionType = 'out' THEN -1 
            ELSE 1 
        END) * Quantity) AS stock
GROUP BY 
    productID, 
    StockLocationID

---

相同，但略为缩短，以消除不必要的乘法：

SELECT 
    productID, 
    StockLocationID,
    SUM(CASE TransactionType 
            WHEN 'out' THEN -Quantity 
            ELSE Quantity 
        END) AS stock
GROUP BY 
    productID, 
    StockLocationID

---

相同，但略为缩短，以消除不必要的乘法：

SELECT 
    productID, 
    StockLocationID,
    SUM(CASE TransactionType 
            WHEN 'out' THEN -Quantity 
            ELSE Quantity 
        END) AS stock
GROUP BY 
    productID, 
    StockLocationID

---

ProductID StockLocationID TransActionType数量谢谢。请帮助我ProductID StockLocationID TransActionType Quantity谢谢。请帮我查一下答案Tim3880谢谢你的答案Tim3880