MySQL

MySQL's slow query log is a key component in your MySQL administration setup. Whilst normal logging can help you in terms of tracking down issues with your database system, the slow query log can help you track down issues in your database setup before they become problematic.

Getting the slow query log set up correctly can help you find and solve issues with slow database queries before they become more problematic. Most slow queries will work fine when there's just a few rows, but as your data grows so will the time taken to find the data. Having the slow query log in place will show these queries and help you do something about them.

Using frameworks to handle the authentication of your PHP application is perfectly fine to do, and normally encouraged. They abstract away all of the complexity of managing users and sessions that need to work in order to allow your application to function.

That said, it is important to take a step back and understand how authentication works in PHP. This allows you to more accurately debug problems with framework authentication systems that you make common use of.

Creating an authentication system using PHP is pretty simple since PHP has many of the features and functions built in. In fact, frameworks will simply wrap this feature set into a coherent authentication model that can be expanded to introduce new features.

In this article I will go through the steps required to create an authentication system using PHP and MariaDB. I will assume you have some knowledge of PHP, but that you want to know more about how to authenticate users.

I needed to create a query that did a case insensitive search using the LIKE command in MySQL and I quickly realised that in order to do this I would need to alter both the parameter and the table data to be the same case. This can be done by using the MySQL UPPER() command on the table data and the strtoupper() PHP function on the input data.

$name = strtoupper('phil');
$query = "SELECT * FROM users WHERE UPPER(forename) LIKE '" . $name . "%'";

This will produce the following SQL query.

SELECT * FROM users WHERE UPPER(forename) LIKE 'P%';

I hope that little tip comes in handy to someone looking for the same solution.

Today I needed to grab some data from a table where there was more than one occurrence of a string within another string. Basically, I needed to find all URL's from a table that were more than 3 levels deep (i.e. with 3 slashes), but realised there wasn't a function to do this in MySQL. I found an alternative method, but it got me thinking on how that might be possible.

Finding the solution wasn't too difficult really, all I needed to do was find out the length of the URL string and then subtract the length of the string with the slashes removed. This MySQL statement will give you the URL and the number of slashes in that URL in a table.

As part of debugging a bit of code I needed to know the longest possible field lengths that a record contains. You might need to know this if you are performing a database migration. The following query returns a field, along with the length of the string, and orders the results by the number of characters in that string.

SELECT field, CHARACTER_LENGTH(field) as fieldCharacterCount
FROM table
ORDER BY fieldCharacterCount DESC

There are quite a few scripts available on the Internet that allow you to dump data from a database into a format that can be used to replicate that database structure elsewhere. The following function is my take on this commonly occurring script.

I use my PC for a lot of different things, and I don't necessarily need to have MySQL server running all the time, especially when I want to play a game. So I wondered if there was a simple way in which I could start and stop the server using a simple .bat file.

I had a look at the MySQL website and found a page that details how to start MySQL from the command line. This page suggested that I use the following command.

"C:\Program Files\MySQL\MySQL Server 5.1\bin\mysqld"

Use the following command to stop the server. In this case the username is root and the password is wibble.

Apache can be set up to log all sorts of information. As of Apache 2.2 the basic log file format that a fresh install of Apache will produce will have the following format:

%h %l %u %t "%r" %>s %b

Which doesn't mean a lot to the uninitiated, so here is a short explanation of each.

A new feature in MySQL version 5.1.6 is the addition of events. These can be either a single event or a schedule, both of which can be given multiple commands to run.

First, you need to make sure that the event scheduler is running. To do this, open up MySQL query browser (or similar) and run the following MySQL command.

SHOW PROCESSLIST;

If the event scheduler you will see a row in the output that looks like this:

Id, User, Host, db, Command, Time, State, Info
120, 'event_scheduler', 'localhost', '', 'Daemon', 242, 'Waiting on empty queue', ''

Turning the event scheduler on and off is quite straightforward and can be done as a MySQL command, or as a parameter when starting the server, or even in an ini file. To turn the scheduler on as a MySQL command run the following:

Sometimes, especially when moving data from one server to another, you might find that you have encoded your MySQL database incorrectly. This problem with first show itself if you have the database encoded in one charset and your website set to display in another. If this is the case then you will find strange characters appearing in your text, especially when using punctuation marks. If you are unable or unwilling to change the character encoding on the site then you need to change how the data is encoded in the database.

The most common sort of thing you might want to do is change from iso-8859-1 (or windows-1252) to UTF-8. This can be done in one of two ways.

The first way is to simply alter the table so that the column contains a different charset.