Calculate Churn Rate

churn_rate.sql

WITH 
[CHURN STAT] AS 
(SELECT *
FROM [TABLE]
WHERE [STAT START] < '[DATE]'
AND (
  ([STAT END] >= '2018-01-01')
  OR ([STAT END]] IS NULL))
),
status AS 
(SELECT 
CASE
  WHEN ([STAT END] > [END DATE])
    OR ([STAT END] IS NULL) THEN 0
  ELSE 1
  END as is_canceled,
CASE
  WHEN ([STAT START] < '2018-01-01')
    AND (
      ([STAT END] >= '2018-01-01')
        OR ([STAT END] IS NULL)
    ) THEN 1
    ELSE 0
  END as is_active
FROM [OTHER TABLE]
)
SELECT 1.0 * SUM(is_canceled)/SUM(is_active) AS churn_rate
FROM status;