Question: how to change date from one format to another in oracle?
Answer: You convert string to date with a different format. Try this. select to_char(to_date('25-SEP-14','DD-MON-YY'), 'DD/MM/YYYY') FROM DUAL. ... 
For a simple test, try this: select to_char(sysdate,'DD/MM/YYYY') "Converted" from dual; ... 
If it is already a data field in the table then use. to_char(date_field,'DD/MM/YYYY')