SELECT
b.userId,
DATE_FORMAT(b.Date, '%Y-%m') AS BillingMonth,
DATE_FORMAT(u.RegistrationDate, '%Y-%m') AS RegistrationMonth,
PERIOD_DIFF(DATE_FORMAT(b.Date, '%Y%m'), DATE_FORMAT(u.RegistrationDate, '%Y%m')) AS MonthsDiff
FROM billing AS b LEFT JOIN users AS u ON b.userId = u.userId
SELECT
COUNT(DISTINCT(b.userId)) AS UsersCount,
DATE_FORMAT(b.Date, '%Y-%m') AS BillingMonth,
DATE_FORMAT(u.RegistrationDate, '%Y-%m') AS RegistrationMonth,
PERIOD_DIFF(DATE_FORMAT(b.Date, '%Y%m'), DATE_FORMAT(u.RegistrationDate, '%Y%m')) AS MonthsDiff
FROM billing AS b LEFT JOIN users AS u ON b.userId = u.userId
GROUP BY BillingMonth, RegistrationMonth, MonthsDiff
SELECT
DATE_ADD(CONCAT(s.RegistrationMonth, '-01'), INTERVAL s.MonthsDiff MONTH) AS time_sec,
SUM(s.Users) AS value,
s.RegistrationMonth AS metric
FROM (
## старый запрос, возвращающий когорты
SELECT
COUNT(DISTINCT(b.userId)) AS Users,
DATE_FORMAT(b.Date, '%Y-%m') AS BillingMonth,
DATE_FORMAT(u.RegistrationDate, '%Y-%m') AS RegistrationMonth,
PERIOD_DIFF(DATE_FORMAT(b.Date, '%Y%m'), DATE_FORMAT(u.RegistrationDate, '%Y%m')) AS MonthsDiff
FROM billing AS b LEFT JOIN users AS u ON b.userId = u.userId
WHERE
u.RegistrationDate BETWEEN '2018-01-01' AND CURRENT_DATE
GROUP BY
BillingMonth, RegistrationMonth, MonthsDiff
) AS s
GROUP BY
time_sec, metric