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Had trouble following this exercise’s solution and tried to do it my way instead, seems to be working too, even tho I wrote way more lines of code, so it’s less efficient I think. Just sharing in case someone might find it usefull.
WITH ret AS (
SELECT DATE(a.created_at) AS d1, COUNT(DISTINCT a.user_id) AS returning_users
FROM gameplays AS a
JOIN gameplays AS b
ON a.user_id = b.user_id
WHERE DATE(b.created_at) = DATE(d1,’+1 day’)
GROUP BY 1),
daily AS(
SELECT DATE(created_at) AS d1, COUNT(DISTINCT user_id) AS daily_users
FROM gameplays
GROUP BY 1)
SELECT ret.d1, ROUND (100 * returning_users / daily_users) AS day_retention
FROM ret
INNER JOIN daily
USING (d1)
GROUP BY 1;
Is there a reason why we use date(datetime(g2.created_at, ‘-1 day’))? Specifically, why we have “datetime” in there? Is this so we can add the modification ‘-1 day’? There isn’t an explanation, though I understand what is happening, as to why we need the datetime function. Thank you to anyone!
I’m not sure there’s a cheatsheet available for this but the best place to look is the SQLite docs (the -1 day syntax is covered under 3. Modifiers on this page)- https://www.sqlite.org/lang_datefunc.html
My code below results in 0.0 for all records in the retention column, I tried a few different variations but I’m not able to get the desired result.
SELECT
date(g1.created_at) as dt
, count(distinct g1.user_id) as total_users
, count(distinct g2.user_id) as retained_users
, 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;
) below.
) to up-vote the contribution!