一个（稍微复杂的）SQL 查询？

Question

我有这个复杂的（对我而言）要求，并希望有一个 SQL 查询。这是交易：

• Access 文件中有一个名为“Expenses”的表。
• 该表包含“类别”、“金额”、“付款人”和“IsShare”等字段。
• 类别可以是燃气、杂货、家庭等...
• 金额是费用的美元金额。
• 付款人可以是我或我的兄弟（“我”或“兄弟”）。
• IsShare 可以为真或假。基本上，如果 IsShare 为真，则费用一分为二。否则，付款人将支付所有费用。

我需要一个 SQL 查询来计算特定类别的所有费用。应该这样计算：

• 我已支付的所有非共享项目的 100%（Payer = 'Me' AND IsShare = false），
• 我已支付的所有共享项目的 50%（Payer = 'Me' AND IsShare = true），并且
• 我兄弟支付的所有共享项目的 50%（Payer = 'Bro' AND IsShare = true）。

查询应该返回所有这三个项目的总和。

到目前为止，我有一个初步查询，但它返回的结果不正确。有人可以帮我改正吗？

非常感谢。

return @"SELECT Sum(Amount) AS TotalAmount " +
        "FROM Expenses " +
        "WHERE Category = 'Groceries' " +
        "AND Payer = 'Me' " +
        "AND Share = false " +
        "GROUP BY Category " +
        "UNION " +
        "SELECT 0.5 * Sum(Amount) AS TotalAmount " +
        "FROM Expenses " +
        "WHERE Category = 'Groceries' " +
        "AND Payer = 'Me' " +
        "AND Share = true " +
        "GROUP BY Category " +
        "UNION " +
        "SELECT 0.5 * Sum(Amount) AS TotalAmount " +
        "FROM Expenses " +
        "WHERE Category = 'Groceries' " +
        "AND Payer = 'Bro' " +
        "AND Share = true ";
        "GROUP BY Category";

Answer 1

我不认为你想要做的事情需要 UNION。这将传递一次数据并将值放在各个列中。您可能需要将 0.5 转换或转换为特定类型，我没有机会运行它。

SELECT 
     Category,
     SUM(CASE WHEN Payer='me' AND NOT IsShare THEN Amount ELSE 0 END) as IPaid,
     SUM(CASE WHEN Payer='me' AND IsShare THEN Amount * 0.5 ELSE 0 END) as SharedPay,
     SUM(CASE WHEN Payer='bro' AND IsShare THEN Amount * 0.5 ELSE 0 END) as BrotherPay
FROM Eexpenses
WHERE Category = 'Groceries'
GROUP BY Category

对于 MS ACCESS：

SELECT 
     Category,
     SUM(IIF(Payer='me' AND NOT IsShare, Amount,0)) as IPaid,
     SUM(IIF(Payer='me' AND IsShare, Amount * 0.5, 0)) as SharedPay,
     SUM(IIF(Payer='bro' AND IsShare, Amount * 0.5, 0)) as BrotherPay
FROM Eexpenses
WHERE Category = 'Groceries'
GROUP BY Category

将三列加在一起：

SELECT Category, IPaid, SharedPay, BrotherPay, IPay + SharedPay + BotherPay as Total 
FROM (
    SELECT 
         Category,
         SUM(IIF(Payer='me' AND NOT IsShare, Amount,0)) as IPaid,
         SUM(IIF(Payer='me' AND IsShare, Amount * 0.5, 0)) as SharedPay,
         SUM(IIF(Payer='bro' AND IsShare, Amount * 0.5, 0)) as BrotherPay
    FROM Eexpenses
    WHERE Category = 'Groceries'
    GROUP BY Category
) as T1