求一SQL语句,

求一SQL语句,高手进，急。
--得到集团编码
SELECT   DISTINCT   jituanbianma     FROM   pls..cust_sls  
WHERE  
--条件1
ref_num   IN(SELECT   cust_num   FROM   pls..customer   WHERE   cust_grade   = 'AA '   AND   is_group=0)  
--条件2
AND   ref_num   IN(SELECT   cust_num   FROM   crm_visit   WHERE   area_code= '3 '     AND   visit_date   NOT   IN(SELECT   riqi   FROM   AM13   WHERE   riqi> = '2007/04/21 '   AND   riqi <= '2007/05/20 '))  
--条件3
AND   jituanbianma   <> ' '  
--条件4
AND   area_code= '3 '


如何修改该SQL语句，加一个假字段   cust_Type，并给cust_Type赋值
达到：

满足(条件2时)   即满足：ref_num   IN(SELECT   cust_num   FROM   crm_visit   WHERE   area_code= '3 '     AND   visit_date   NOT   IN(SELECT   riqi   FROM   AM13   WHERE   riqi> = '2007/04/21 '   AND   riqi <= '2007/05/20 '))  

cust_Type= 'T '

不满足(条件2时)   即不满足：ref_num   IN(SELECT   cust_num   FROM   crm_visit   WHERE   area_code= '3 '     AND   visit_date   NOT   IN(SELECT   riqi   FROM   AM13   WHERE   riqi> = '2007/04/21 '   AND   riqi <= '2007/05/20 '))  

cust_Type= 'F '


高手急救。




------解决方案--------------------
我也不知道你是什么数据，姑且这样吧：
select jituanbianma,max(cust_Type)
from(
SELECT DISTINCT jituanbianma,
case when exists(SELECT 1 FROM crm_visit WHERE area_code= '3 ' AND visit_date NOT IN(SELECT riqi FROM AM13 WHERE riqi> = '2007/04/21 ' AND riqi <= '2007/05/20 ') and cust_num=a.ref_num) then 'T '
else 'F '
end cust_Type
FROM pls..cust_sls a
WHERE
ref_num IN(SELECT cust_num FROM pls..customer WHERE cust_grade = 'AA ' AND is_group=0)
AND jituanbianma <> ' '
AND area_code= '3 '
)bb
group by jituanbianma