sql 判断

 case when  条件  then  操作 else  操作   end

举例：
       select t.*,(select count(*) mobcount from mob_bas_role_agent a where a.role_id=t.role_id) clientcount,(select count(*) from mob_bas_role_agent d where d.role_id=t.role_id and d.send_flag=1 ) clientsendcount,
case when t.role_type<1 then (select count(*) from mob_mcc_stat_fit b where b.role_id=t.role_id) else (select count(*) from mob_mcc_stat_stable c where c.role_id=t.role_id) end finishClientCount
          from (select re.*, rownum rownum_
              from (select r.role_id, r.role_name, r.role_type, r.flag
                      from mob_bas_role r
                     where r.username ='username'
                     and r.flag != 9
                     order by r.indate desc) re) t
                     where t.rownum_ between 1 and 5