How the FROM_DAYS() function works in Mariadb?

The MariaDB FROM_DAYS() function is used to convert a day count (the number of days since the year 0) to a DATE value. It is particularly useful for performing date calculations and manipulations within a database environment.

Syntax

The syntax for the MariaDB FROM_DAYS() function is as follows:

FROM_DAYS(N)

• N: A required parameter that represents the day count (number of days since the year 0) to be converted to a DATE value.

The function returns a DATE value corresponding to the day count specified by the N parameter. If the input value is NULL or falls outside the valid range for dates, the function returns NULL.

Examples

Example 1: Converting a day count to a date

This example demonstrates how to use the FROM_DAYS() function to convert a day count to a date.

SELECT FROM_DAYS(735670);

The output of this statement is:

+-------------------+
| FROM_DAYS(735670) |
+-------------------+
| 2014-03-13        |
+-------------------+

The day count 735670 represents the number of days since the year 0, which corresponds to the date 2015-07-04.

Example 2: Converting a negative day count

This example shows how the FROM_DAYS() function handles negative day counts.

SELECT FROM_DAYS(-365);

The output of this statement is:

+-----------------+
| FROM_DAYS(-365) |
+-----------------+
| 0000-00-00      |
+-----------------+

A negative day count represents a date before the year 0. In this case, -365 corresponds to the date 0000-00-00, which is the earliest possible date in the Gregorian calendar system.

Example 3: Handling invalid day counts

This example demonstrates how the FROM_DAYS() function handles invalid day counts.

SELECT FROM_DAYS(NULL);

The output of this statement is:

+-----------------+
| FROM_DAYS(NULL) |
+-----------------+
| NULL            |
+-----------------+

If the input day count is NULL, the FROM_DAYS() function returns NULL as well.

Example 4: Using FROM_DAYS() in a date calculation

This example illustrates how the FROM_DAYS() function can be used in date calculations.

DROP TABLE IF EXISTS employees;
CREATE TABLE employees (
    id INT PRIMARY KEY,
    name VARCHAR(255),
    hire_date DATE
);

INSERT INTO employees (id, name, hire_date) VALUES
    (1, 'John Doe', FROM_DAYS(737000)),
    (2, 'Jane Smith', FROM_DAYS(736800));

SELECT name, hire_date, DATE_ADD(hire_date, INTERVAL 365 DAY) AS anniversary
FROM employees;

The output of this statement is:

+------------+------------+-------------+
| name       | hire_date  | anniversary |
+------------+------------+-------------+
| John Doe   | 2017-11-02 | 2018-11-02  |
| Jane Smith | 2017-04-16 | 2018-04-16  |
+------------+------------+-------------+

In this example, we create a table employees and insert two records with hire dates calculated using the FROM_DAYS() function. We then use FROM_DAYS() in combination with DATE_ADD() to calculate the anniversary date for each employee, which is one year after their hire date.

Example 5: Combining with other date functions

This example shows how the FROM_DAYS() function can be used in combination with other date functions.

SELECT FROM_DAYS(DATEDIFF('2023-05-01', '2022-01-01'));

The output of this statement is:

+-------------------------------------------------+
| FROM_DAYS(DATEDIFF('2023-05-01', '2022-01-01')) |
+-------------------------------------------------+
| 0001-04-30                                      |
+-------------------------------------------------+

Here, we use the DATEDIFF() function to calculate the number of days between '2022-01-01' and '2023-05-01', which is 486. We then pass this day count to the FROM_DAYS() function, which converts it back to the corresponding date '0001-04-30'.

Related Functions

The following are some functions related to the MariaDB FROM_DAYS() function:

• MariaDB TO_DAYS() function is used to convert a DATE value to the corresponding day count (number of days since the year 0).
• MariaDB DATE() function is used to extract the date part from a DATE or DATETIME value.
• MariaDB DATEDIFF() function is used to calculate the number of days between two dates.

Conclusion

The MariaDB FROM_DAYS() function is a valuable tool for converting day counts to DATE values, which is essential for various date-related operations and calculations in a database environment. By understanding its syntax, usage, and related functions, developers can effectively manipulate and work with date data in their MariaDB applications. The function’s ability to handle both positive and negative day counts, as well as its compatibility with other date functions, makes it a versatile and powerful utility in date and time management tasks.