10. SQLServer : 表达式

-- 语法
--Simple CASE expression:   
CASE input_expression   
     WHEN when_expression THEN result_expression [ ...n ]   
     [ ELSE else_result_expression ]   
END   

--Searched CASE expression:  
CASE  
     WHEN Boolean_expression THEN result_expression [ ...n ]   
     [ ELSE else_result_expression ]   
END  

-- 示例一
SELECT   ProductNumber, Category =  
      CASE ProductLine  
         WHEN 'R' THEN 'Road'  
         WHEN 'M' THEN 'Mountain'  
         WHEN 'T' THEN 'Touring'  
         WHEN 'S' THEN 'Other sale items'  
         ELSE 'Not for sale'  
      END,  
   Name  
FROM Production.Product  
ORDER BY ProductNumber;  
GO  


--示例二
SELECT   ProductNumber, Name, "Price Range" =   
      CASE   
         WHEN ListPrice =  0 THEN 'Mfg item - not for resale'  
         WHEN ListPrice < 50 THEN 'Under $50'  
         WHEN ListPrice >= 50 and ListPrice < 250 THEN 'Under $250'  
         WHEN ListPrice >= 250 and ListPrice < 1000 THEN 'Under $1000'  
         ELSE 'Over $1000'  
      END  
FROM Production.Product  
ORDER BY ProductNumber ;