sql语言中有没有类似C语言中的switch case的语句？？

  没有,用case   when   来代替就行了.   
       
  例如,下面的语句显示中文年月   
    
  select   getdate()   as   日期,case   month(getdate())   
  when   11   then   '十一'   
  when   12   then   '十二'   
  else   substring('一二三四五六七八九十',   month(getdate()),1)   
  end+'月'   as   月份

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CASE 可能是 SQL 中被误用最多的关键字之一。虽然你可能以前用过这个关键字来创建字段，但是它还具有更多用法。例如，你可以在 WHERE 子句中使用 CASE。
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http://www.cnblogs.com/Images/OutliningIndicators/None.gif首先让我们看一下 CASE 的语法。在一般的 SELECT 中，其语法如下： 
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http://www.cnblogs.com/Images/OutliningIndicators/None.gifSELECT <</span>myColumnSpec> = 
http://www.cnblogs.com/Images/OutliningIndicators/None.gifCASE 
http://www.cnblogs.com/Images/OutliningIndicators/None.gifWHEN <</span>A> THEN <</span>somethingA> 
http://www.cnblogs.com/Images/OutliningIndicators/None.gifWHEN <</span>B> THEN <</span>somethingB> 
http://www.cnblogs.com/Images/OutliningIndicators/None.gifELSE <</span>somethingE> 
http://www.cnblogs.com/Images/OutliningIndicators/None.gifEND 
http://www.cnblogs.com/Images/OutliningIndicators/None.gif 
http://www.cnblogs.com/Images/OutliningIndicators/None.gif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： 
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http://www.cnblogs.com/Images/OutliningIndicators/None.gifUSE pubs 
http://www.cnblogs.com/Images/OutliningIndicators/None.gifGO 
http://www.cnblogs.com/Images/OutliningIndicators/None.gifSELECT 
http://www.cnblogs.com/Images/OutliningIndicators/None.gif     Title, 
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    'Price Range' = 
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    CASE 
http://www.cnblogs.com/Images/OutliningIndicators/None.gif        WHEN price IS NULL THEN 'Unpriced' 
http://www.cnblogs.com/Images/OutliningIndicators/None.gif        WHEN price <</span> 10 THEN 'Bargain' 
http://www.cnblogs.com/Images/OutliningIndicators/None.gif        WHEN price BETWEEN 10 and 20 THEN 'Average' 
http://www.cnblogs.com/Images/OutliningIndicators/None.gif        ELSE 'Gift to impress relatives' 
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    END 
http://www.cnblogs.com/Images/OutliningIndicators/None.gifFROM titles 
http://www.cnblogs.com/Images/OutliningIndicators/None.gifORDER BY price 
http://www.cnblogs.com/Images/OutliningIndicators/None.gifGO 
http://www.cnblogs.com/Images/OutliningIndicators/None.gif 
http://www.cnblogs.com/Images/OutliningIndicators/None.gif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： 
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http://www.cnblogs.com/Images/OutliningIndicators/None.gifSELECT 'Number of Titles', Count(*) 
http://www.cnblogs.com/Images/OutliningIndicators/None.gifFROM titles 
http://www.cnblogs.com/Images/OutliningIndicators/None.gifGROUP BY 
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    CASE 
http://www.cnblogs.com/Images/OutliningIndicators/None.gif        WHEN price IS NULL THEN 'Unpriced' 
http://www.cnblogs.com/Images/OutliningIndicators/None.gif        WHEN price <</span> 10 THEN 'Bargain' 
http://www.cnblogs.com/Images/OutliningIndicators/None.gif        WHEN price BETWEEN 10 and 20 THEN 'Average' 
http://www.cnblogs.com/Images/OutliningIndicators/None.gif        ELSE 'Gift to impress relatives' 
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    END 
http://www.cnblogs.com/Images/OutliningIndicators/None.gifGO 
http://www.cnblogs.com/Images/OutliningIndicators/None.gif 
http://www.cnblogs.com/Images/OutliningIndicators/None.gif你甚至还可以组合这些选项，添加一个 ORDER BY 子句，如下所示： 
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http://www.cnblogs.com/Images/OutliningIndicators/None.gifUSE pubs 
http://www.cnblogs.com/Images/OutliningIndicators/None.gifGO 
http://www.cnblogs.com/Images/OutliningIndicators/None.gifSELECT 
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    CASE 
http://www.cnblogs.com/Images/OutliningIndicators/None.gif        WHEN price IS NULL THEN 'Unpriced' 
http://www.cnblogs.com/Images/OutliningIndicators/None.gif        WHEN price <</span> 10 THEN 'Bargain' 
http://www.cnblogs.com/Images/OutliningIndicators/None.gif        WHEN price BETWEEN 10 and 20 THEN 'Average' 
http://www.cnblogs.com/Images/OutliningIndicators/None.gif        ELSE 'Gift to impress relatives' 
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    END AS Range, 
http://www.cnblogs.com/Images/OutliningIndicators/None.gif     Title 
http://www.cnblogs.com/Images/OutliningIndicators/None.gifFROM titles 
http://www.cnblogs.com/Images/OutliningIndicators/None.gifGROUP BY 
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    CASE 
http://www.cnblogs.com/Images/OutliningIndicators/None.gif        WHEN price IS NULL THEN 'Unpriced' 
http://www.cnblogs.com/Images/OutliningIndicators/None.gif        WHEN price <</span> 10 THEN 'Bargain' 
http://www.cnblogs.com/Images/OutliningIndicators/None.gif        WHEN price BETWEEN 10 and 20 THEN 'Average' 
http://www.cnblogs.com/Images/OutliningIndicators/None.gif        ELSE 'Gift to impress relatives' 
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    END, 
http://www.cnblogs.com/Images/OutliningIndicators/None.gif     Title 
http://www.cnblogs.com/Images/OutliningIndicators/None.gifORDER BY 
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    CASE 
http://www.cnblogs.com/Images/OutliningIndicators/None.gif        WHEN price IS NULL THEN 'Unpriced' 
http://www.cnblogs.com/Images/OutliningIndicators/None.gif        WHEN price <</span> 10 THEN 'Bargain' 
http://www.cnblogs.com/Images/OutliningIndicators/None.gif        WHEN price BETWEEN 10 and 20 THEN 'Average' 
http://www.cnblogs.com/Images/OutliningIndicators/None.gif        ELSE 'Gift to impress relatives' 
http://www.cnblogs.com/Images/OutliningIndicators/None.gif    END, 
http://www.cnblogs.com/Images/OutliningIndicators/None.gif     Title 
http://www.cnblogs.com/Images/OutliningIndicators/None.gifGO 
http://www.cnblogs.com/Images/OutliningIndicators/None.gif 
http://www.cnblogs.com/Images/OutliningIndicators/None.gif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。 
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http://www.cnblogs.com/Images/OutliningIndicators/None.gif除了选择自定义字段之外，在很多情况下 CASE 都非常有用。再深入一步，你还可以得到你以前认为不可能得到的分组排序结果集。

参考连接 http://www.cnblogs.com/eshizhan/archive/2012/04/06/2435493.html