MySQL DAYOFMONTH Function

The DAYOFMONTH function in MySQL is a powerful tool that can be used to extract the day of the month from a given date. This function is especially useful for performing operations related to date data types in SQL databases. Understanding how to use this function can greatly enhance your ability to work with dates in your database applications.

1. Introduction

The DAYOFMONTH function returns the day of the month from a date, represented as an integer between 1 and 31. For example, if you have a date like ‘2023-10-05’, the function would return 5. This functionality is vital in various use cases, such as generating reports by day or filtering records based on the day of a specific month.

2. Syntax

The syntax for the DAYOFMONTH function is straightforward:

DAYOFMONTH(date)

Parameters:

• date: This is the date from which you want to extract the day of the month. It can be either a date string or a date column from a table.

3. Return Value

The DAYOFMONTH function returns an integer value corresponding to the day of the month. Here are some possible return values based on different date inputs:

Date Input	Return Value (DAYOFMONTH)
‘2023-10-05’	5
‘2023-11-15’	15
‘2023-12-31’	31
‘2023-01-01’	1

4. Example

Let’s look at a simple example that demonstrates how to use the DAYOFMONTH function in a SQL query:

SELECT DAYOFMONTH('2023-10-05') AS DayOfMonth;

This query will return:

DayOfMonth
5

Now, let’s see how this function can be applied to a database table. Assume we have a table named orders with the following structure:

CREATE TABLE orders (
        id INT PRIMARY KEY,
        order_date DATE
    );

We can insert some sample data into the orders table:

INSERT INTO orders (id, order_date) VALUES 
    (1, '2023-10-05'),
    (2, '2023-11-15'),
    (3, '2023-12-31');

Now, we can extract the day of the month from each order date:

SELECT id, order_date, DAYOFMONTH(order_date) AS DayOfMonth
    FROM orders;

This query will output the following result:

ID	Order Date	DayOfMonth
1	2023-10-05	5
2	2023-11-15	15
3	2023-12-31	31

5. Related Functions

There are several functions related to DAYOFMONTH which you may find useful:

• DAYOFWEEK(date): Returns the day of the week for a given date (1 for Sunday to 7 for Saturday).
• DAYOFYEAR(date): Returns the day of the year for a given date (1 to 366).
• MONTH(date): Returns the month from a given date (1 to 12).
• YEAR(date): Extracts the year from a given date.

6. Conclusion

In summary, the DAYOFMONTH function in MySQL is an essential tool for anyone working with dates in a database. Its ability to return the day of the month makes it invaluable for a wide range of applications, from creating reports to filtering data. As you continue to explore MySQL, be sure to investigate other date functions that can further enhance your data manipulation capabilities.

FAQ

What will DAYOFMONTH(NULL) return?

It will return NULL.

Can I use DAYOFMONTH with a date stored in a variable?

Yes, you can use DAYOFMONTH with date variables just like with any date string or column.

What format should the date be in?

The date should be in a valid MySQL date format, such as ‘YYYY-MM-DD’.

Can I use DAYOFMONTH in a WHERE clause?

Yes, you can use this function as part of a WHERE clause to filter records based on the day of the month.