Question

我有代码，我需要将过滤器添加到where子句中，该子句根据变量的值而变化。如下例所示，如果@X的值为0，那么我想要包括OrderID = 10的过滤器;否则我想为OrderID = 20添加过滤器，而DepartmentID的另一个过滤器为NULL或值为30.这可以使用IF ELSE完成，如下所示

DECLARE @X INT

-- Retrieve value for @X

IF @X = 0 
BEGIN
    SELECT *
    FROM Customers
    WHERE ProductID IS NOT NULL
    AND OrderID = 10
END
ELSE
BEGIN
    SELECT *
    FROM Customers
    WHERE ProductID IS NOT NULL
    AND OrderID = 20 AND ( DepartmentID IS NULL OR DepartmentID = 30)
END

我想知道是否有使用一个SQL语句进行此操作。我认为在WHERE中使用CASE是可行的，但SQL似乎不允许在下面。

SELECT *
    FROM Customers
    WHERE ProductID IS NOT NULL
    AND CASE WHEN @X = 0 THEN OrderID = 10 ELSE OrderID = 20 AND ( DepartmentID IS NULL OR DepartmentID = 30) END

有没有完成这个。

Answer 1

你很亲密，

AND OrderID = (CASE WHEN @X = 0 THEN 10 ELSE 20 END)
AND DepartmentID = (CASE WHEN @X = 0 THEN DepartmentID ELSE 30 END)

Answer 2

您可以在没有CASE的情况下执行此操作：

SELECT *
FROM Customers
WHERE ProductID IS NOT NULL
AND ((@X = 0 AND OrderID = 10) OR (@X <> 0 AND OrderID = 20 AND DepartmentID = 30))

编辑：

根据您要添加的条件：

SELECT *
FROM Customers
WHERE ProductID IS NOT NULL
AND ((@X = 0 AND OrderID = 10) OR (@X <> 0 AND OrderID = 20 AND (DepartmentID IS NULL OR DepartmentID = 30)))

Answer 3

SELECT *
FROM Customers
WHERE ProductID IS NOT NULL
AND OrderID = CASE WHEN @X = 0 THEN 10 ELSE 20 END
AND ISNULL(DepartmentID,30) = CASE WHEN @X = 0 THEN ISNULL(DepartmentID,30)  ELSE 30 END

在WHERE中使用CASE

3 个答案:

编辑：