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. (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. (more…)
Man, what a week it has been. As you may have noticed it’s been a few days too many since my last post. The reason for that is a hectic week at work has prevented me from having time.
Now that the week is over and it was hectic because of my own stupidity, I mine as well write an article about it to save you some time. (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. (more…)