Logo         Community
The Company
Your Account
Contact Us
Date Arithmetic With MySQL
Simplify date and time arithmetic with built-in MySQL functions.

| When Two And Two Don't Make Four |

When dealing with temporal data, one of the more common (and complex) tasks involves performing addition and subtraction operations on date and time values. Consider, for example, the simple task of calculating a date 91 days hence. Usually, in order to do this with any degree of precision, you need to factor in a number of different variables: the month you're in, the number of days in that month, the number of days in the months following, whether or not the current year is a leap year, and so on.

Writing code to perform such calculations quickly becomes both tedious and complicated. What is really needed in such situations is a date API that supports such date arithmetic, one that takes care of the numerous minor adjustments that have to be made when adding and subtracting intervals to date and time values.

Fortunately, MySQL comes with just such an API, in the form of six functions designed specifically to perform calculations on date and time values. Here they are:

TO_DAYS() - calculates the day number corresponding to a specific date

FROM_DAYS() - calculates the date corresponding to a day number

DATE_ADD() - adds a specified interval to a date and returns a new date

DATE_SUB() - subtracts a specified interval from a date and returns a new date

PERIOD_DIFF() - calculates the difference (in months) between two dates

PERIOD_ADD() - adds an interval (in months) to a date and returns a new date

Let's take a closer look.

How to do Everything with PHP & MySQL
How to do Everything with PHP & MySQL, the best-selling book by Melonfire, explains how to take full advantage of PHP's built-in support for MySQL and link the results of database queries to Web pages. You'll get full details on PHP programming and MySQL database development, and then you'll learn to use these two cutting-edge technologies together. Easy-to-follow sample applications include a PHP online shopping cart, a MySQL order tracking system, and a PHP/MySQL news publishing system.

Read more, or grab your copy now!

previous page more like this  print this article  next page
In trog...
Logging With PHP
Building A Quick-And-Dirty PHP/MySQL Publishing System
Output Buffering With PHP
Date/Time Processing With PHP
Creating Web Calendars With The PEAR Calendar Class
In the hitg report...
Crime Scenes
Animal Attraction
Lord Of The Strings
In boombox...
Patience - George Michael
Think Tank - Blur
My Private Nation - Train
In colophon...
Hostage - Robert Crais
The Dead Heart - Douglas Kennedy
Right As Rain - George Pelecanos
In cut!...
American Chai
The Core
Find out how you can use this article on your own Web site!

Copyright © 1998-2018 Melonfire. All rights reserved
Terms and Conditions | Feedback