SELECT <myColumnSpec> =

CASE

WHEN <A> THEN <somethingA>

WHEN <B> THEN <somethingB>

ELSE <somethingE>

END  

在上面的代码中需要用具体的参数代替尖括号中的内容。下面是一个简单的例子： 

USE pubs

GO

SELECT

    Title,

    'Price Range' =

    CASE

        WHEN price IS NULL THEN 'Unpriced'

        WHEN price < 10 THEN 'Bargain'

        WHEN price BETWEEN 10 and 20 THEN 'Average'

        ELSE 'Gift to impress relatives'

    END

FROM titles

ORDER BY price

GO  

这是 CASE 的典型用法，但是使用 CASE 其实可以做更多的事情。比方说下面的 GROUP BY 子句中的 CASE： 

SELECT 'Number of Titles', Count(*)

FROM titles

GROUP BY

    CASE

        WHEN price IS NULL THEN 'Unpriced'

        WHEN price < 10 THEN 'Bargain'

        WHEN price BETWEEN 10 and 20 THEN 'Average'

        ELSE 'Gift to impress relatives'

    END

GO  

你甚至还可以组合这些选项，添加一个 ORDER BY 子句，如下所示： 

USE pubs

GO

SELECT

    CASE

        WHEN price IS NULL THEN 'Unpriced'

        WHEN price < 10 THEN 'Bargain'

        WHEN price BETWEEN 10 and 20 THEN 'Average'

        ELSE 'Gift to impress relatives'

    END AS Range,

    Title

FROM titles

GROUP BY

    CASE

        WHEN price IS NULL THEN 'Unpriced'

        WHEN price < 10 THEN 'Bargain'

        WHEN price BETWEEN 10 and 20 THEN 'Average'

        ELSE 'Gift to impress relatives'

    END,

    Title

ORDER BY

    CASE

        WHEN price IS NULL THEN 'Unpriced'

        WHEN price < 10 THEN 'Bargain'

        WHEN price BETWEEN 10 and 20 THEN 'Average'

        ELSE 'Gift to impress relatives'

    END,

    Title

GO  

注意，为了在 GROUP BY 块中使用 CASE，查询语句需要在 GROUP BY 块中重复 SELECT 块中的 CASE 块。