размер члена структуры [дубликата]

Изменение запроса Бена немного,

 select count(distinct switch_id)   
  from xx_new.xx_cti_call_details@appsread.prd.com  
 where dealer_name =  'XXXX'    
   and creation_date between add_months(trunc(sysdate,'mm'),-1) and last_day(add_months(trunc(sysdate,'mm'),-1))