TeddyPerkins

MongoDB Cheat Sheet

show dbs

Magic words:

psql -U postgres

Some interesting flags (to see all, use -h or --help depending on your psql version):

-E: will describe the underlaying queries of the \ commands (cool for learning!)
-l: psql will list all databases and then exit (useful if the user you connect with doesn't has a default database, like at AWS RDS)

	--[[
	$Id$

	Copyright © 2007-2018 the VideoLAN team

	This program is free software; you can redistribute it and/or modify
	it under the terms of the GNU General Public License as published by
	the Free Software Foundation; either version 2 of the License, or
	(at your option) any later version.

	CREATE TABLE large_test (num1 bigint, num2 double precision, num3 double precision);

	INSERT INTO large_test (num1, num2, num3)
	SELECT round(random()10), random(), random()142
	FROM generate_series(1, 20000000) s(i);

	EXPLAIN (analyse, buffers)
	SELECT num1, avg(num3) as num3_avg, sum(num2) as num2_sum
	FROM large_test
	GROUP BY num1;