CONNECT:
jonathan AT jonmaas DOT com +1-310-500-5841

SQL

Here are a few of my favorite SQL queries. 

/* Find what tables are in a Postgre SQL Database */

SELECT * FROM pg_catalog.pg_tables;

/* Churn Rate */

/* Churn rate SQL Query – note you must fill in your own column and table names */

SELECT COUNT(DISTINCT user_id) AS enrollments,
	COUNT(CASE
       	WHEN strftime("%m", cancel_date) = '03'
        THEN user_id
  END) AS march_cancellations,
 	ROUND(100.0 * COUNT(CASE
       	WHEN strftime("%m", cancel_date) = '03'
        THEN user_id
  END) / COUNT(DISTINCT user_id)) AS churn_rate
FROM pro_users
WHERE signup_date < '2017-04-01'
	AND (
    (cancel_date IS NULL) OR
    (cancel_date > '2017-03-01')
  );

/* Select the count of a unique value in a table */

SELECT COUNT(DISTINCT column_name)
as what_you_want_to_call_it
FROM table_name;

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