Flipflops.org » MySQL

MySQL DATE_FORMAT() AND PHP date() formats

Flipflops — Tue, 01 Dec 2009 20:21:11 +0000

I’m always finding myself looking up strings to format PHP and MySQL dates. A simple d/m/Y is pretty straight forward but sometimes things can get a bit fiddly. Where ever possible I try and leave my date formatting in the database, but I still find myself doing it in PHP all the time.

Here are a few simple cut and paste date formats.

PHP Date	MySQL Date	PHP Format	MySQL Format	Notes
7/9/2009	7/9/2009	j/n/Y	%e/%c/%Y
07/09/2009	07/09/2009	d/m/Y	%d/%m/%Y
7/9/2009 8:07	7/9/2009 8:07	j/n/Y G:i	%e/%c/%Y %k:%i
7/9/2009 8:07 AM	7/9/2009 8:07 AM	j/n/Y G:i A	%e/%c/%Y %k:%i %p
07/09/2009 8:07 AM	07/09/2009 8:07 AM	d/m/Y G:i A	%d/%m/%Y %k:%i %p
07/09/2009 08:07 AM	07/09/2009 08:07 AM	d/m/Y H:i A	%d/%m/%Y %H:%i %p
07/09/2009 8:07 am		d/m/Y G:i a
Mon 7th Sep 2009	Mon 7th Sep 2009	D jS M Y	%a %D %b %Y
Monday 7th September 2009	Monday 7th September 2009	l jS F Y	%W %D %M %Y
2009-09-07T08:07:50+01:00	Monday 7th September 2009	Y-m-d\TH:i:sP	%W %D %M %Y	PHP DATE_ATOM constant
Mon, 07 Sep 2009 08:07:50 +0100	Mon, 07 Sep 2009 08:07:50	D, d M Y H:i:s O	%a, %d %b %Y %T	PHP DATE_RSS constant

The PHP way

 
echo(date('d/m/Y', strtotime('2009-09-07 08:07:50')));
 
//or
 
$dateTime = new DateTime("now");
echo $dateTime->format("Y-m-d H:i:s")

The MySQL way

 
$sqlstring = "SELECT DATE_FORMAT('2009-09-07 08:07:50', '%d/%m/%Y') AS formated_date FROM some_table" ;

If you haven’t looked at the PHP manual closely for a while you should definitely (re)acquaint yourself with the DateTime Class.

UK Towns and Postcode Areas

Flipflops — Tue, 18 Nov 2008 19:55:04 +0000

The other day I needed a list of UK post towns matched up to postcode areas, which I found on wikipedia.

Anyway I have tidied it up and put it into two database tables postcode and town

You can download the SQL file here towns.zip

Hope it comes in useful.

Finding overlapping dates and times in MySQL

Flipflops — Thu, 01 May 2008 21:04:40 +0000

Quite often you end up in situations where you are required to check and see if one time period overlaps another time period. Probably the most common situation this occurs in is when you are building a booking system – be it for tables or cars or rooms.

You have a series of entries in a database with a start (date)time and an end (date)time and before adding a new record you need to check that it doesn’t overlap with another booking.

The solution is fairly simple but I always end up making a quick diagram on a piece of paper to check.

As you can see two time periods can either be sequential (i.e. there is no overlap at all) or they can overlap in one of four ways. Put this into a diagram and the solution becomes pretty obvious.

There is an overlap if end_time_1 > start_time_2 AND start_time_1 < end_time_2

Time	start_1	start_2	end_1	end_2	end_1 > start_2	start_1 < end_2
1	09:00	08:00	11:00	10:00	true	true
2	09:00	10:00	11:00	12:00	true	true
3	09:00	08:00	11:00	12:00	true	true
4	09:00	09:30	11:00	10:30	true	true
5	09:00	07:00	11:00	08:00	false	true
6	09:00	12:00	11:00	13:00	true	false

An example SQL query would be something like the one below but make sure your datetime formats are correct – in MySQL the default format is YYYY-MM-DD hh:mm:ss

 
SELECT * FROM bookings WHERE room_id = '" . $room_id . "' AND ((date_end > '" . $start_date . "') AND (date_start < '" . $end_date . "')) ";

The above query will pull back the records where the times overlap.

MySQL import / export at the Command Line

Flipflops — Wed, 19 Mar 2008 21:11:10 +0000

Like many (most?) developers when I work with a database I tend to manage them using another programme – usually either phpMyAdmin or Navicat. However there are times when you have to get basic again and dig down to the Command Line (usually because of an access issue like a firewall setting you can’t change or because you need to import a file too big for phpMyAdmin). The trouble is if you only use these commands once in a blue moon you soon forget them.

Dump (export your database)

Login to the shell or Command Prompt, navigate to where you would like your file saved.
mysqldump --user=your_username --password=your_password your_database > your_dump_file.sql

Where:
your_username is a mysql user with the correct rights to the database you want to dump.
your_password is the password for your_username.
your_database is the name of your database.
your_dump_file.sql is the name of the file that will be created in the export.

Import

Create the database that you want to import into, but leave it empty or if you are using an existing database remove the tables (make sure you have a backup first).
Login to the shell or Command Prompt
mysql --user=your_username --password=your_password your_database < your_file_to_import.sql