Default fields in PostgreSQL in OpenERP v7.

I have some issue regarding date field like create_date, write_date in OpenERP v7. 1: How OpenERP creating id, create_uid, create_date, write_uid and write_date by default in each module. 2: How can i insert my customize date into create_date field. 3: How can i retrieve all fields, both default and defined fields. Like select * from table_name. Please provide me some suggestion. Thank you ..!