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sqlÓïÑÔÖÐÓÐûÓÐÀàËÆCÓïÑÔÖеÄswitch caseµÄÓï¾ä£¿£¿
  ûÓÐ,ÓÃcase   when   À´´úÌæ¾ÍÐÐÁË.  
      
  ÀýÈç,ÏÂÃæµÄÓï¾äÏÔʾÖÐÎÄÄêÔ  
   
  select   getdate()   as   ÈÕÆÚ,case   month(getdate())  
  when   11   then   'ʮһ'  
  when   12   then   'Ê®¶þ'  
  else   substring('Ò»¶þÈýËÄÎåÁùÆß°Ë¾ÅÊ®',   month(getdate()),1)  
  end+'ÔÂ'   as   Ô·Ý
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CASE ¿ÉÄÜÊÇ SQL Öб»ÎóÓÃ×î¶àµÄ¹Ø¼ü×ÖÖ®Ò»¡£ËäÈ»Äã¿ÉÄÜÒÔǰÓùýÕâ¸ö¹Ø¼ü×ÖÀ´´´½¨×ֶΣ¬µ«ÊÇËü»¹¾ßÓиü¶àÓ÷¨¡£ÀýÈ磬Äã¿ÉÒÔÔÚ WHERE ×Ó¾äÖÐʹÓà CASE¡£
 
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SELECT <myColumnSpec> =
CASE
WHEN <A> THEN <somethingA>
WHEN <B> THEN <somethingB>
ELSE <somethingE>
END
 
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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
 
ÕâÊÇ CASE µÄµäÐÍÓ÷¨£¬µ«ÊÇʹÓà CASE Æäʵ¿ÉÒÔ×ö¸ü¶àµÄÊÂÇé¡£±È·½ËµÏÂÃæµÄ GROUP BY ×Ó¾äÖÐµÄ CASE£º
 
SELECT 'Number of Titles', Count(*)
from titles
GROUP BY
    CASE
        WHEN price IS NULL THEN 'Unpriced'
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go
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SQL 92 ±ê×¼ YoYo

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from table_source
[WHERE search_condition]
[GROUP BY group_by_expression]
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