sql分區間顯示數據

用sql語句實現分年齡段查詢數據，語句如下：

SELECT sl.region,COUNT(DISTINCT(intervieweeID)) num
FROM    
(
    SELECT  
        intervieweeID,
        CASE    
            WHEN   (age>=75)              THEN   '75以上' 
            WHEN   (age>=65 AND age<=74)    THEN    '65-74' 
            WHEN   (age>=55 AND age<=64)    THEN    '55-64' 
            WHEN   (age>=45 AND age<=54)    THEN    '45-54' 
            WHEN   (age>=35 AND age<=44)    THEN    '35-44' 
            WHEN   (age>=25 AND age<=34)    THEN    '25-34'                   
            WHEN   (age>=17 AND age<=24)     THEN    '17-24'  
            ELSE     'age unknow'
        END  AS region
    FROM 

         interviewee
) sl GROUP BY sl.region