Oracle date function for the previous month

Question

I have the query below where the date is hard-coded. My objective is to remove the harcoded date; the query should pull the data for the previous month when it runs.

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Answer 1

Modifying Ben's query little bit,

 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))