Select query for Difference in day in a date time field mysql table

Day of the month can be collected from the date and time field by using the function day(). This will return day in number format and we can apply calculation to this. Note that this will not take care of month and year, for example the difference in days between 12th July 04 and 14th July 05 is two days only.
Syntax

DAY(date)

Example

SELECT DAY('2016-07-27');

Output is 27

DAYNAME(): Day Name in Full ( Monday )

We will use one PHP Script to get the current date by using DAYNAME()

For easy understanding we will create one PHP page with this query with all other fields.

Yesterday , Today and Tomorrow

SELECT DAY(CURDATE()- interval 1 day)  as YesterDay, DAY(CURDATE()) as Today, DAY(CURDATE()+ interval 1 Day) as Tomorrow

YesterDay	Today	Tomorrow
21	22	23

PHP Script

To display the above details we used PHP Script, you can use the same script for using all above queries.

config.php connection string is available here

PDO for executing Queries in PHP

How to get records using FETCH() are here

<?Php
require 'config.php';  // Database connection string
$query='SELECT DAY(CURDATE()- interval 1 day)  as YesterDay, DAY(CURDATE()) as Today, DAY(CURDATE()+ interval 1 Day) as Tomorrow';
// Change the above Query part to get different results // 

$count=$dbo->prepare($query);
$count->execute();
$row = $count->fetch(PDO::FETCH_OBJ);
echo "
<table class='table table-striped'>
<tr class='info'><td>YesterDay</td><td>Today</td><td>Tomorrow</td></tr>
<tr><td>$row->YesterDay</td><td>$row->Today</td><td>$row->Tomorrow</td></tr>
</table>";

?>

The basic query for MySQL table is here

SELECT day(dt2) FROM `dt_tb`

This will collect the day part from the field

Difference in Day

The sql query is modified to display all the columns with the days and their difference for easy comparison. Here is the query used.
Note that this is only math difference between two day ( numbers ) only and to get differece in dates we have to use TO_DAYS()

<?Php
require "config.php";// Database connection

$query="SELECT dt,dt2,day(dt) as day1,day(dt2)as day2,(day( dt2 ) - day( dt )) as difference FROM `dt_tb` ";

if($stmt = $connection->query("$query")){

  echo "No of records : ".$stmt->num_rows."<br>";

  echo "<table class='table table-striped'>
<tr class='info'> <th> dt</th><th> dt2</th><th>day1</th><th>day2</th><th>Difference</th></tr>";
while ($row = $stmt->fetch_assoc()) {
 echo "<tr><td>$row[dt]</td><td>$row[dt2]</td><td>$row[day1]</td><td>$row[day2] </td><td>$row[difference] </td></tr>";
 }
echo "</table>";
}else{
echo $connection->error;
}
?>

The output of this query is here

dt	dt2	day1	day2	difference
2004-10-26 00:00:00	2005-01-25	26	25	-1
2004-05-05 23:56:25	2005-06-12	5	12	7
2005-12-08 13:20:10	2005-06-06	8	6	-2

Here is the sql code to create and fill the table with records

CREATE TABLE IF NOT EXISTS `dt_tb` (
  `id` int(2) NOT NULL AUTO_INCREMENT,
  `dt` datetime NOT NULL DEFAULT '0000-00-00 00:00:00',
  `dt2` date NOT NULL DEFAULT '0000-00-00',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB  DEFAULT CHARSET=utf8 AUTO_INCREMENT=4 ;

--
-- Dumping data for table `dt_tb`
--

INSERT INTO `dt_tb` (`id`, `dt`, `dt2`) VALUES
(1, '2004-10-26 00:00:00', '2005-01-25'),
(2, '2004-05-05 23:56:25', '2005-06-12'),
(3, '2005-12-08 13:20:10', '2005-06-06');

DAY() : function in a mysql date and time field

Yesterday , Today and Tomorrow

PHP Script

Difference in Day