DAYOFWEEK

PostgreSQL equivalent:

Returns the weekday number of a date, counting from Sunday.

MySQL 8.1

DAYOFWEEK(date)

Parameters

An integer from 1 to 7, where 1 is Sunday and 7 is Saturday; NULL for an incomplete date (2022-00-00) and for an unrecognized value

MySQL 8.1

SELECT DAYOFWEEK('2022-06-16');

DAYOFWEEK('2022-06-16')
5

MySQL 8.1

SELECT payment_id,
	date,
	DAYOFWEEK(date) AS weekday_number
FROM Payments
WHERE DAYOFWEEK(date) IN (1, 7);

To number the days from Monday (1 is Monday, 7 is Sunday), use WEEKDAY(date) + 1.