Postgres HowTos

To login

sudo su - postgres
psql
\l #lists databases
\connect database_name #to connect to that database 
\dt #lists tables

To quit

\q
exit #to get out of the postgres user

To drop tables from Postgres, documentation here

You generally need to do this when there is some problem with migrations, and you need to drop a table so a migration can build it.

DROP TABLE table_name CASCADE; #to drop a table, cascades and deletes dependencies

To add tables to Postgres, documentation here

In general, you shouldn't need to do this. This should always be done with migrations. Remember, you can write SQL migrations.