Altering table with plugin

I have to construct a plugin which alters the piwik_log_link_visit_action to add an extra column which stores the parentId from where it is called.

If my constructed plugin, alters the table with desired value. Does, all the previous mapping of piwik_log_link_visit_action stay?

Like all previous mappings are inserted and parentId inserted as well?

Or do I have to duplicate all insert commands defined previously and then append my custom insertions?

Please guide.