小编use*_*361的帖子

UPDATE dbo.TestStudents  
SET LASTNAME = 
( CASE  
WHEN (LASTNAME = 'AAA') THEN 'BBB' 
WHEN (LASTNAME = 'CCC') THEN 'DDD' 
WHEN (LASTNAME = 'EEE') THEN 'FFF' 
ELSE  (LASTNAME)
END )

该语句适用于此目的,但else条件扫描表中的每条记录.有什么方法可以保留未受影响的行吗？