How to calculate the weekday index from a given date using the WEEKDAY() function?

WEEKDAY(date) is a MySQL built-in function that returns the weekday index from a given date. For example:

SELECT WEEKDAY(NOW()), DAYOFWEEK(NOW()), DAYNAME(NOW()), NOW();
  -- +----------------+------------------+----------------+---------------------+
  -- | WEEKDAY(NOW()) | DAYOFWEEK(NOW()) | DAYNAME(NOW()) | NOW()               |
  -- +----------------+------------------+----------------+---------------------+
  -- |              3 |                5 | Thursday       | 2023-11-16 08:05:56 |
  -- +----------------+------------------+----------------+---------------------+

Reference information of the WEEKDAY() function:

WEEKDAY(date): int
  Returns the weekday index for date (0 = Monday, 1 = Tuesday, … 6 = Sunday).

Arguments, return value and availability:
  date: Required. The date to extract the weekday index from.
  int: Return value. The weekday index.
  Available since MySQL 4.

Related MySQL functions:

• DAYOFWEEK() - Day of Week (1=Sunday)

⇒ WEEKOFYEAR() - Calendar Week of Year

⇐ WEEK() - Week of Year

⇑ MySQL Functions on Date and Time

⇑⇑ MySQL Function References