FAQ: Common Metrics - 1 Day Retention 3

This community-built FAQ covers the “1 Day Retention 3” exercise from the lesson “Common Metrics”.

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This exercise can be found in the following Codecademy content:

SQL: Analyzing Business Metrics

FAQs on the exercise 1 Day Retention 3

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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!

5 Likes

Why we must use “date(datetime(g2.created_at” instead of use “date(g2.created_at”?

Even i am unable to understand this modification date(datetime(g2.created_at, ‘-1 day’)
Is there any cheat sheet for this?? datetime with this -1 day

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