How to see size of postgres databases / tables

Tables:

SELECT pg_tables.tablename, pg_tables.schemaname, pg_size_pretty(pg_relation_size((pg_tables.schemaname::text || '.'::text) || pg_tables.tablename::text)) AS pg_size_pretty FROM pg_tables ORDER BY pg_relation_size((pg_tables.schemaname::text || '.'::text) || pg_tables.tablename::text) DESC;

Database entirely (I swear I had this sites statistics script somewhere that contained all this, including a MySQL version.. where did that go?):

select pg_database.datname, pg_size_pretty(pg_database_size(pg_database.datname)) AS size from pg_database WHERE pg_database.datname = 'foobar';