Build cohort 30-day retention from signup date

Using only the company table (below), compute a monthly cohorted 30-day retention rate based on signup_date. Define cohort_month = DATE_TRUNC('month', signup_date). An account is "retained at day 30" if termination_date IS NULL OR termination_date > signup_date + INTERVAL '30 days'. Include only cohorts for which signup_date + 30 days is fully observable (right-censoring): parameterize a data_cutoff_date (e.g., the max of GREATEST(MAX(signup_date), MAX(termination_date), MAX(subscription_date))) and exclude cohorts where cohort_month + INTERVAL '30 days' > data_cutoff_date. Return: cohort_month (DATE), cohort_size (INT), retained_30d (INT), retention_30d_rate (DECIMAL, 4 decimals). Then, generalize to a "monthly retention curve" by adding retained_60d and retained_90d (and their rates) using a generate_series of day thresholds (30, 60, 90) and pivoting/widening the results. company +------------+-------------+-------------------+------------------+ | company_id | signup_date | subscription_date | termination_date | +------------+-------------+-------------------+------------------+ | 1 | 2019-05-20 | 2019-06-02 | 2020-01-10 | | 2 | 2019-06-15 | 2019-06-20 | NULL | | 3 | 2019-07-01 | 2019-07-05 | 2019-12-31 | | 4 | 2020-06-10 | 2020-06-11 | NULL | | 5 | 2020-06-30 | 2020-07-02 | NULL | | 6 | 2020-07-15 | NULL | NULL | +------------+-------------+-------------------+------------------+ Edge cases to handle explicitly: - termination_date exactly equals signup_date + 30 days is NOT retained. - Null termination_date implies retained at any threshold (subject to censoring rule). - Ensure companies without subscription_date are still counted in the signup-based cohort and evaluated for retention status. - Present rates as retained_xxd / cohort_size with safe division and 0.0 when cohort_size = 0.