Syntax:
DAYNAME(date)

Returns the name of the weekday for date. The language used for the
name is controlled by the value of the lc_time_names system variable
(see https://dev.mysql.com/doc/refman/8.0/en/locale-support.html).
Returns NULL if date is NULL.

URL: https://dev.mysql.com/doc/refman/8.0/en/date-and-time-functions.html

