To obtain the AMP database schema, run the following command on your AMP:
pg_dump -U airwave -W airwave --schema-only > amp_schema
This will dump the schema to the text file amp_schema, which you can then pull off the AMP with WinSCP, etc.
Note that AMP's database schema often changes with each release. AMP also stores data in files under the /var/airwave/ directory, including the RRD files that contain bandwidth, signal quality, user count, and other time-series data.