If you are not familiar with database indexes or even if you are, but not sure when to use them, this article will be perfect for you.
In this article, I will show you an example of a simple query without an index and then that same query again with the index. I am certain that you will be shocked by the difference.
I’ll continue today with another good database programming article. If you missed yesterdays, you may view it here.
Today’s article will discuss when to use a static COUNT() versus a dynamic COUNT(). On a regular basis we are tasked with creating a message center or a photo album and we need to display a count of new messages or pictures in the album.
The obvious solution is to do a simple query: SELECT COUNT(*) FROM pictures WHERE album_id = 1 and display the result beside our album name. Now, let’s assume that we allow multiple albums our actual query would be closer to this: SELECT albums.*, COUNT(pictures.*) as picture_count FROM albums INNER JOIN pictures ON albums.id = pictures.album_id WHERE albums.id = 1. This will of course work, but let me show you a better, more practical approach that will improve performance significantly on large databases. Read more »
Quite often we get a complaint from a client that their homepage is too slow. The first thing we do is load the homepage up and see for ourselves. Yep, it looks slow, so the next step is too see what is being done. Quite often you’ll see some random data being displayed on the homepage. Whether it’s random news articles, photos, videos, etc…If this is not the case, you may find my article on improving slow loading web pages more useful.
If the homepage is slow because of random data, you can lay a bet with high certainty that those 10 random articles are being pulled with an ORDER BY RAND() OR NEWID() slowing the site to a crawl. In case you are curious the difference, RAND() is the MySQL way and NEWID() is the SQL Server way. In this article, I’ll show you why you should avoid these functions and several different solutions to help you overcome this issue. Read more »
Recently on a project I was working on, I was tasked with fixing drag and drop that was terribly slow. The drag and drop was implemented with scriptaculous on a calendar system. When you clicked an event to drag it it took about 5 seconds before the page would actually let you drag it! This was clearly unacceptable and it has to be possible because Google Calendar is lightening fast.
The first thing I did was download and setup jquery to see if it was related to how scriptaculous was created. After setting up jquery, it was just as slow. This lead me to believe that it was a fundamental problem with how the drag and drop was set up in both libraries. Read more »
The following article is going to be short and sweet, but applying this technique will help you move up those all important rankings.
The technique involves updating your <title> tag. With a few simple changes, your ranking for your targetted keywords will begin to immediately climb (well not immediately, but next time Google crawls your web page). Read more »
When you do SQL queries do you find yourself always, or almost always, using left joins? If you’ve answered yes to this question, I would suggest to continue to read and understand some downfalls that you might be getting yourself into.
Let’s start by looking at a standard query that has a left join:
SELECT * FROM users u LEFT JOIN countries c ON c.id = u.country_id WHERE u.id = 5
The following query will return all fields from the users table and all fields from the countries table. Now you’re thinking, “Yeah, looks good, so what’s wrong with this?”. Well, I’m glad you asked. Read more »
This article is a continuation to my article about Firebug. YSlow is an add-on to Firebug that helps developers determine why a site is loading slowly.
After you install YSlow, if you open up Firebug in Mozilla a new tab will now appear called “YSlow”. The next steps would be to load a web site that you want to check it’s performance. After the web site has loaded, click the YSlow tab, if the results don’t compile automatically, click the Performance button to run the diagnostics.
The grading is made up of 13 steps. For each step you receive a grade from A to F. An overall grade is compiled in the same format. Read more »