If you don't need to know changes in the file you can just use a column with an update date (you can use triggers for this or edit your column like: `tm` timestamp NOT NULL default CURRENT_TIMESTAMP on update CURRENT_TIMESTAMP
). You could also store a number of "edit times" to see if it's the same as the number of months since the creation of the row.
Otherwise, you should write a new row for every update and keep track of the user by an ID.
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