the original : http://www.linuxscrew.com/2009/07/03/postgresql-show-tables-show-databases-show-columns/
mysql: SHOW TABLES
postgresql: \d
postgresql: SELECT table_name FROM information_schema.tables WHERE table_schema = 'public';
mysql: SHOW DATABASES
postgresql: \l
postgresql: SELECT datname FROM pg_database;
mysql: SHOW COLUMNS
postgresql: \d table
postgresql: SELECT column_name FROM information_schema.columns WHERE table_name ='table';
mysql: DESCRIBE TABLE
postgresql: \d+ table
postgresql: SELECT column_name FROM information_schema.columns WHERE table_name ='table';