I know how to make custom fields for my custom post types. I also know there is the
Advanced Custom Fieldsplugin.
But I need to know how I can store my custom fields in my custom post type to my custom DB tables. I've been looking for tutorials, but I only find how to create SQL tables in plugins.
How can I fetch "my data" (and save it in my own tables) and at the same time save the other data for the page the normal way?