MySQL na PostgreSQL:Jak upravit tento SQL dotaz?

SELECT 
  extract(MONTH from created_at) AS month, 
  extract(YEAR from created_at) AS year 
FROM users 
GROUP BY extract(MONTH from created_at), extract(YEAR from created_at) 
ORDER BY extract(MONTH from created_at), extract(YEAR from created_at) 

Zde je aktuální manuál
http://www.postgresql.org/docs/current/static/functions-datetime.html#FUNCTIONS-DATETIME-EXTRACT

Btw:Toto je standardní (ANSI) SQL, který funguje také na MySQL.