In MariaDB, DAYOFWEEK() is a built-in date and time function that returns the day of the week from a given date.
It accepts one argument, which is the date you want to extract the day of the week from.
It returns the day as a number. The index numbering adheres to the ODBC standard (1 = Sunday, 2 = Monday, etc). This is in contrast to WEEKDAY(), where 0 = Monday, 1 = Tuesday, etc.
Syntax
The syntax goes like this:
DAYOFWEEK(date)Where date is the date to get the day from.
Example
Here’s an example:
SELECT DAYOFWEEK('2030-01-25');Result:
+-------------------------+
| DAYOFWEEK('2030-01-25') |
+-------------------------+
| 6 |
+-------------------------+
Compared with the Day Name
Here’s another one, alongside DAYNAME() to return the day name:
SELECT
DAYOFWEEK('2030-01-20'),
DAYNAME('2030-01-20');Result:
+-------------------------+-----------------------+
| DAYOFWEEK('2030-01-20') | DAYNAME('2030-01-20') |
+-------------------------+-----------------------+
| 1 | Sunday |
+-------------------------+-----------------------+
As mentioned, the index numbering starts at 1 for Sunday.
Here’s Saturday:
SELECT
DAYOFWEEK('2030-01-19'),
DAYNAME('2030-01-19');Result:
+-------------------------+-----------------------+
| DAYOFWEEK('2030-01-19') | DAYNAME('2030-01-19') |
+-------------------------+-----------------------+
| 7 | Saturday |
+-------------------------+-----------------------+
Datetime Values
It also works with datetime values:
SELECT DAYOFWEEK('2030-01-24 10:30:45');Result:
+----------------------------------+
| DAYOFWEEK('2030-01-24 10:30:45') |
+----------------------------------+
| 5 |
+----------------------------------+
Zero Days
Zero days result in null.
Example:
SELECT DAYOFWEEK('2030-00-00');Result:
+-------------------------+
| DAYOFWEEK('2030-00-00') |
+-------------------------+
| NULL |
+-------------------------+
Numeric Dates
It’s also possible to pass dates as a number, as long as it makes sense as a date.
Example
SELECT DAYOFWEEK(20300125);Result:
+---------------------+ | DAYOFWEEK(20300125) | +---------------------+ | 6 | +---------------------+
Or even the following (which uses a two-digit year):
SELECT DAYOFWEEK(300125);Result:
+-------------------+ | DAYOFWEEK(300125) | +-------------------+ | 6 | +-------------------+
But it must make sense as a date. Here’s what happens if I increase the day part to an invalid day:
SELECT DAYOFWEEK(20300135);Result:
+---------------------+ | DAYOFWEEK(20300135) | +---------------------+ | NULL | +---------------------+
Other Delimiters
You can use other delimiters for the date. MariaDB is quite forgiving when it comes to delimiters on dates. Here are some valid examples:
SELECT
DAYOFWEEK('2030/01/25'),
DAYOFWEEK('2030,01,25'),
DAYOFWEEK('2030:01:25'),
DAYOFWEEK('2030;01!25');Result (using vertical output):
DAYOFWEEK('2030/01/25'): 6
DAYOFWEEK('2030,01,25'): 6
DAYOFWEEK('2030:01:25'): 6
DAYOFWEEK('2030;01!25'): 6
Current Date
We can pass NOW() as the date argument to use the current date:
SELECT
NOW(),
DAYOFWEEK(NOW());Result:
+---------------------+------------------+ | NOW() | DAYOFWEEK(NOW()) | +---------------------+------------------+ | 2021-05-15 09:17:44 | 7 | +---------------------+------------------+
Invalid Arguments
When passed an invalid argument, DAYOFWEEK() returns null:
SELECT DAYOFWEEK('Homer');Result:
+--------------------+
| DAYOFWEEK('Homer') |
+--------------------+
| NULL |
+--------------------+
Missing Argument
Calling DAYOFWEEK() with the wrong number of arguments, or without passing any arguments, results in an error:
SELECT DAYOFWEEK();Result:
ERROR 1582 (42000): Incorrect parameter count in the call to native function 'DAYOFWEEK'
And another example:
SELECT DAYOFWEEK('2030-01-25', '2045-05-08');Result:
ERROR 1582 (42000): Incorrect parameter count in the call to native function 'DAYOFWEEK'