MySQL DAYOFWEEK function is one of the MySQL Date Functions, used to return the weekday index value of the given date. This DAYOFWEEK function returns value from 1 to 7 where 1 = Sunday, 2 = Monday, ….. 7 = Sunday.
Let us see how to use this DAYOFWEEK function to get the weekday or Day of Week in MySQL from an expression with example. The basic syntax of the DAYOFWEEK() Function in MySQL is as shown below:
DAYOFWEEK(date or expression);
MySQL DAYOFWEEK function Example
These examples help you understand the use of the dayofweek function. Here, we are returning the Weekday index number from the date expression, and the Date & time expression.
SELECT DAYOFWEEK('2018-12-30');
SELECT DAYOFWEEK('2018-12-31');
SELECT DAYOFWEEK('2018-12-15 03:22:19');
Let us see another example of the MySQL DAYOFWEEK function. Here, we are returning the Weekday index number from the current date and time returned by the Now() and CURDATE() function.
SELECT DAYOFWEEK(NOW()), DAYOFWEEK(CURRENT_DATE());
MySQL DAYOFWEEK Function Example 2
The following MySQL queries show what happens when we try to return the weekday index from 0 date format, string format, or invalid dates.
SELECT DAYOFWEEK(NOW() + 2);
SELECT DAYOFWEEK('2019-02-31');
SELECT DAYOFWEEK('0000-00-00');
From the above screenshot, DAYOFWEEK(‘2019-02-31’); statement returned NULL because it’s an invalid date. Within the Last Date Function statement, DAYOFWEEK(0) means, we are trying to extract the day of the week from a zero date part. That’s why it returns NULL.