The **`DAYOFWEEK()`** function returns the weekday index from a date sent as a parameter. 

Figure 1 shows a visual representation of the `DAYOFWEEK()` function and the week index.

# Syntax
```sql
DAYOFWEEK(date)
```
# Parameter
The `DAYOFWEEK()` function takes the date as a parameter. 
> The date must be in the format YYYY-MM-DD, or else this function returns `NULL`.

# Return value
The `DAYOFWEEK()` function returns the week index from a date sent as a parameter.  
> It returns `NULL` if the date is invalid.


# Code





-- current date  
SELECT DAYOFWEEK(NOW());

-- invalid month
SELECT DAYOFWEEK('2021-0-12');

-- valid month/day
SELECT DAYOFWEEK('2021-05-03');

-- invalid day
SELECT DAYOFWEEK('2021-2-30');

What is DAYOFWEEK() in SQL?

DAYOFWEEK() function returns the weekday index from a valid date parameter in SQL.