How to use the MySQL FROM_DAYS() function

The FROM_DAYS() function in MySQL converts a day number to a DATE value. It is useful for calculating dates based on an integer day number.

Syntax

The basic syntax of FROM_DAYS() is:

FROM_DAYS(day_number)

Where day_number is an integer day number to be converted to a DATE.

Examples

Here are some examples of using FROM_DAYS() in MySQL:

1. Get the date for day number 735000:

   SELECT FROM_DAYS(735000);
   
   // Output: 2012-05-12
   

2. Calculate a date 90 days from now:

   SELECT FROM_DAYS(TO_DAYS(NOW()) + 90);
   
   // Output: 2023-02-12 (90 days from today)
   

3. Get the day of week for a given day number:

   SELECT DAYNAME(FROM_DAYS(735030));
   
   // Output: Sunday
   

4. Calculate dates based on day numbers in a table:

   SELECT FROM_DAYS(day_num) AS date
   FROM records;
   

5. Get the number of days between two dates:

   SELECT TO_DAYS('2023-02-15') - TO_DAYS('2023-01-01');
   
   // Output: 45
   

Other Similar Functions

• TO_DAYS(): Converts a DATE value to a day number
• DATEDIFF(): Calculates the number of days between two dates
• DATE_ADD() and DATE_SUB(): Add and subtract days from a date

So in summary, FROM_DAYS() converts day numbers to DATE values for date calculations.