The SQL problem you've described involves calculating the user retention rate based on a defined cohort. Let's break down how to approach this step-by-step, ensuring we understand each part clearly.
Step 1: Define the Cohort
Firstly, let's define what a "cohort" is in this context:
- A cohort consists of users who first logged into an application on a specific date or within a specific time period (e.g., week).
To find the cohort for each user, we need to determine their earliest login date. This can be done using MIN(login_date) GROUP BY user_id.
sql1WITH user_cohorts AS ( 2 SELECT 3 user_id, 4 MIN(login_date) AS first_login, 5 DATE_TRUNC('week', MIN(login_date))::date AS week_cohort 6 FROM logins 7 GROUP BY user_id 8) 9SELECT * FROM user_cohorts;
This query creates a Common Table Expression (CTE) named user_cohorts that contains each user's earliest login date and the corresponding week cohort.
Step 2: Calculate Retained Users
Next, we need to identify which users from our defined cohorts returned within
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