Codecademy SQL: Analyzing Business Metrics Exercise 13 of 14

--first answer

select
  date(g1.created_at) as dt,
  g1.user_id,
  g2.user_id
from gameplays as g1
  join gameplays as g2 on
    g1.user_id = g2.user_id
    and date(g1.created_at) = date(datetime(g2.created_at, '-1 day'))
order by 1
limit 100;

--second answer

select
  date(g1.created_at) as dt,
  count(distinct g1.user_id) as total_users,
  count(distinct g2.user_id) as retained_users
from gameplays as g1
  left join gameplays as g2 on
    g1.user_id = g2.user_id
    and date(g1.created_at) = date(datetime(g2.created_at, '-1 day'))
group by 1
order by 1
limit 100;

--third answer

select
  date(g1.created_at) as dt,
  round(100 * count(distinct g2.user_id) /
    count(distinct g1.user_id)) as retention
from gameplays as g1
  left join gameplays as g2 on
    g1.user_id = g2.user_id
    and date(g1.created_at) = date(datetime(g2.created_at, '-1 day'))
group by 1
order by 1
limit 100;