Question

我遇到了一个难于解决的情况：

WHEN @CustomerID = 3 AND @OrderID = 2 AND @Name IN ('Hello') THEN 'Regular'
WHEN @CustomerID = 3 AND @OrderID = 2 AND @Telephone = 1 AND @Name IN ('Hello') THEN 'Business'

如果我有两个语句，它仅返回“ Regular”，但是如果我取出“ Regular”，则显示“ Business”。我在做什么错了？

Answer 1

如果您想要一个或两个，则需要是两个单独的列，或者如果您想在单个列中同时包含两个输出：

要么：

case WHEN @CustomerID = 3 AND @OrderID = 2 AND @Name IN ('Hello') THEN 'Regular' end,
case WHEN @CustomerID = 3 AND @OrderID = 2 AND @Telephone = 1 AND @Name IN ('Hello') THEN 'Business' end

或：

WHEN @CustomerID = 3 AND @OrderID = 2 AND @Telephone = 1 AND @Name IN ('Hello') THEN 'Regular, Business' 
WHEN @CustomerID = 3 AND @OrderID = 2 AND @Name IN ('Hello') THEN 'Regular'

Answer 2

返回的值将是匹配的最早WHEN子句（按文本形式）的THEN表达式的值。

在您的查询中，Second WHEN子句包含First WHEN子句的一部分。这意味着，只要Second为true，First WHEN子句就为true。因此，最早的（First）WHEN子句将返回THEN表达式。

查询1：

SELECT CASE WHEN @CustomerID = 3 AND @OrderID = 2 AND @Name IN ('Hello') THEN 'Regular'
WHEN @CustomerID = 3 AND @OrderID = 2 AND @Telephone = 1 AND @Name IN ('Hello') THEN 'Business' END

查询2：

SELECT CASE WHEN @CustomerID = 3 AND @OrderID = 2 AND @Telephone = 1 AND @Name IN ('Hello') THEN 'Business'
WHEN @CustomerID = 3 AND @OrderID = 2  AND @Name IN ('Hello') THEN 'Regular' END

输入：

@CustomerID INT=3
@OrderID INT = 2
@Name VARCHAR(100)='Hello'
@Telephone INT=1

输出：

Query1 : 'Regular'
Query1 : 'Business'

输入：

@CustomerID INT=3
@OrderID INT = 2
@Name VARCHAR(100)='Hello'
@Telephone INT=0

输出：

Query1 : 'Regular'
Query1 : 'Regular'

案例表达式只显示一次

2 个答案: