i am creating a new “Bookings” custom post type in wordpress . And I already have a table in Mysql database set up where I am filling date from ,date to and the room name . My problem is that I want to have an option from the admin pannel to add new book to edit existing books etc etc. .But i dont know where(where to write php code for this) to start interacting with mysql to display that results in the admin panel .
The approach you are following will consume too much time. Try using “Custom Types” plugins, there are plenty of good plugins in this category, and the normal way they operate is that they deal with the new added fields as custom fields, stored in postmeta and bound to posts, to utilize all post action filters and handlers. Your attempt means that you will recreate all of these filters and handlers that by the end should be bound to wordpress triggers and events.
Watch the following video tutorial for one of the available custom types plugins, to understand the concept, once you have it, try search the available plugins to choose the one that fully suits your needs: