Question

我是SQL的新手，并尝试在我的SQL语句中创建一个子查询，该子查询查找别名列中所有总计的总和。我对如何格式化子查询感到有点困惑，每次我尝试它都说我格式化不正确。

 cmd.CommandText = "SELECT ProductName, OD.UnitPrice, Quantity, OD.UnitPrice * Quantity AS total, SUM(SELECT(total)) AS finalTotal " +
            "FROM Products, [Order Details] AS OD " +
            "WHERE OD.ProductID = Products.ProductID AND orderID = @OrderID";

如果我尝试上面的代码，我会收到一条错误，说我在SELECT语句附近有不正确的语法。任何帮助表示赞赏！

Answer 1

如果您需要获取所有行的总和，可以SUM使用OVER

SELECT *,SUM(total)OVER() AS finalTotal
FROM
  (
    SELECT P.ProductName, OD.UnitPrice, Quantity, OD.UnitPrice * OD.Quantity AS total
    FROM Products P
    JOIN [Order Details] OD ON OD.ProductID = Products.ProductID
    WHERE OD.orderID = @OrderID
  ) q

Answer 2

问题出在SUM(SELECT(total))，你不能以这种方式调用select，你必须指定from子句来创建一个子查询。

如果您需要获得所有行的总和（单价*数量），那么：

SELECT Sum (UnitPrice * Quantity) AS total FROM Products
JOIN [Order Details] OD ON OD.ProductID = Products.ProductID
WHERE OD.orderID = @OrderID

如果你需要为记录集重复这一点，那么：

SELECT *,SUM(total)OVER() AS OverAllTotal
FROM
  (
    SELECT P.ProductName, OD.UnitPrice, Quantity, OD.UnitPrice * OD.Quantity AS total
    FROM Products P
    JOIN [Order Details] OD ON OD.ProductID = Products.ProductID
    WHERE OD.orderID = @OrderID
  ) subQuery

获取别名列总和的SQL子查询

2 个答案: