Child theme functions.php file change database entries

You shouldn’t need to change anything in the database. If you’ve set up your child theme correctly, and it appears in the list of installed themes, activating that child theme, should make any updates necessary. The customizations you made back in the day should go in the child functions.php and child style.css. As long as the function names and class names haven’t been changed in the original the child theme files should overwrite the parent theme.