SELECT installs.game AS "Game",
TO_CHAR(installs.installed_at,'YYYY-mm-dd') AS "Installed at",
COUNT(DATE_PART('day',sessions.created_at-installs.installed_at)) AS "User",
DATE_PART('day',sessions.created_at-installs.installed_at) AS "Day"
FROM installs
INNER JOIN sessions
ON installs.user_id = sessions.user_id
GROUP BY installs.game,
installs.installed_at,installs.user_id,DATE_PART('day',sessions.created_at-installs.installed_at)
ORDER BY installs.installed_at;