Where is the group of a fields group stored in datababase (to get it programatically)? I have installed the Field group module, which, as the name implies, groups fields together. Once you have ordered the fields of content type, is there any way to programmatically get the group of the fields that are grouped together?

I have search in database (columns field_config, field_config_instance) and there is not any column to save that information. Where is that information (the group of field) stored in database?

Thanks in advance.
I have never used field_group module, but your approach seems wrong, looking in the database doesn't help often.
I suggest you should install the module devel, turn it on.
Then use the function dsm() to see the content of your node/form that you are in.
If I assume you are in the hook_form_submit() to process something, dsm($form_state), if you are in another hook with a node as parameter of your hook, just dsm($node), you might find what you are looking for.

Cheers