Subscription Retention

Given a table of subscriptions, write a query to get the retention rate of each monthly cohort for each plan_id for the three months after sign-up.

Order your output by start_month, plan_id, then num_month.

If an end_date is in the same month as start_date we say the subscription was not retained in the first month.

If the end_date occurs in the month after the month of start_date, the subscription was not retained in the second month. And so on for the third.

The end_date field is NULL if the user has not canceled.

Example:

Input:

subscriptions table

Output: