MySQL Cookbook

Performing Calculations with TIMESTAMP Values

Problem

You want to calculate intervals between TIMESTAMP values, search for records based on a TIMESTAMP column, and so forth.

Solution

TIMESTAMP values are susceptible to the same kinds of date calculations as DATETIME values, such as comparison, shifting, and component extraction.

Discussion

The following queries show some of the possible operations you can perform on TIMESTAMP values, using the tsdemo2 table from Recipe 5.34:

• Records that have not been modified since they were created:

  SELECT * FROM tsdemo2 WHERE t_create = t_update;

• Records modified within the last 12 hours:

  SELECT * FROM tsdemo2 WHERE t_update >= DATE_SUB(NOW( ),INTERVAL 12 HOUR);

• The difference between the creation and modification times (here expressed both in seconds and in hours):

  SELECT t_create, t_update,
  UNIX_TIMESTAMP(t_update) - UNIX_TIMESTAMP(t_create) AS 'seconds',
  (UNIX_TIMESTAMP(t_update) - UNIX_TIMESTAMP(t_create))/(60 * 60) AS 'hours'
  FROM tsdemo2;

• Records created from 1 PM to 4 PM:

  SELECT * FROM tsdemo2
  WHERE HOUR(t_create) BETWEEN 13 AND 16;

  Or:

  SELECT * FROM tsdemo2
  WHERE DATE_FORMAT(t_create,'%H%i%s') BETWEEN '130000' AND '160000';

  Or even by using TIME_TO_SEC( ) to strip off the date part of the t_create values:

  SELECT * FROM tsdemo2
  WHERE TIME_TO_SEC(t_create)
  BETWEEN TIME_TO_SEC('13:00:00') AND TIME_TO_SEC('16:00:00');