Database: 1. How can I get list of ALL fields and 2. Dump of field entries

General query:
1. I’d like to see a list of ALL the database fields against my theme so I don’t accidentally create unnecessary custom fields.

2. How can I get a ‘dump’ of all entries against a specific field. e.g. I’d like to see a list of all ‘first_names’ for user profiling etc etc.

Any help is greatly appreciated.

Mike