I have a built in form I created on my WP website . I want to store the inputs to a table on my DB. All tutorials that explane how to create a talke include the fact that I have to create a plugin for that.

All my functions are written in functions.php and I prefer to write the function that creates the DB there too.

If I write the function that creates the table in functions.php - will it make multiple tables or something like that? or does it work only once?

can I just create one using PHPMYADMIN ? or it will not include the built-in wordpress security ect'?