T-SQL中的SQL Server CASE语句

Question

您好我正在处理涉及必须使用CASE的查询。我不断收到错误，但无法弄清楚原因。以下是我所尝试过的。

SELECT 

    CASE 

    when LineItem like '%Apple%' THEN ProductType = 'Apple' 
    when LineItem like '%Orange' THEN ProductType = 'Orange' 
    when LineItem like '%Strawberry' THEN ProductType = 'Red' 
    when ProductType like 'Yellow' THEN ProductType 
    else ProductType = 'White' 

    end as ProductType 

FROM Fruits 

我得到的错误是在“=”符号上。 在T-SQL中的WHEN关键字之后不可能有两个不同的列吗？

Answer 1

尝试像这样...

SELECT 
    ProductType = CASE 
         WHEN f.LineItem like '%Apple%' THEN 'Apple' 
         WHEN f.LineItem like '%Orange' THEN 'Orange' 
         WHEN f.LineItem like '%Strawberry' THEN 'Red' 
         WHEN f.ProductType like 'Yellow' THEN f.ProductType 
         ELSE 'White' 
        END 
FROM 
    dbo.Fruits f; 

Answer 2

只是语法错误。无需Then ProductType = '...'

SELECT 
    CASE 
    when LineItem like '%Apple%' THEN 'Apple' 
    when LineItem like '%Orange' THEN 'Orange' 
    when LineItem like '%Strawberry' THEN 'Red' 
    when ProductType like 'Yellow' THEN ProductType 
    else 'White' 
    end as ProductType 
FROM Fruits