select t.employee_code, 
       (t.first_name || '  ' || t.last_name) name, 
       add_months(t.date_of_joining, 120) as mature_date
  from employee t, employee_type et
 where et.employee_type = t.employee_type
   AND et.description = 'REGULAR'
   AND mature_date >= '11-oct-2011'
   AND ET.POST = 1
   AND T.POST  = 1;


  

select t.employee_code, 
       (t.first_name || '  ' || t.last_name) name
 from employee t, employee_type et
 where et.employee_type = t.employee_type
   AND et.description = 'REGULAR'
   AND add_months(t.date_of_joining, 120) >= To_date('11-10-2011','DD-MM-YYYY')
   AND ET.POST = 1
   AND T.POST  = 1;