Most likely there is the structure of the database enables this behavior: when you save the data not update in database are replaced and a new row is added.
The simplest structure with minimal number of required fields looks like this:
— article_id (non-unique)
Accordingly when you save the add a new row with the same ID, but more fresh timestampa. During selection — take the most recent (queries with grouping, any additional field being updated with a flag to pefomance).