#0103

Cohort Month Zero

MediumSQL25 min20 XP

Problem

Given events(user_id, event_date), return user_id and cohort_month, the YYYY-MM of each user first event. Sort by user_id.

Cohorts start with a first-seen date. Retention and lifecycle analysis build on this step.

events(user_id INTEGER, event_date TEXT)

Example 1

Inputuser 1 events in Jan and Feb

Outputuser 1 cohort_month Jan

Cohort is based on the first event date.

CodeSQL

SELECT
  -- write your code here
  user_id
FROM events;

SELECT
  -- write your code here
  user_id
FROM events;

Visible browser tests run here when available.

Testcases1 visible / 3 hidden categories

Core example

Inputuser 1 events in Jan and Feb

Expecteduser 1 cohort_month Jan

Cohort is based on the first event date.

Hidden Test Categories

one event per userunordered eventssame first month ties