Wednesday, October 31, 2007

The Pac-Man joke

I just love this joke by the comedian Marcus Brigstocke:

If Pac-Man had affected us as kids, we'd all be running around in dark rooms, munching pills and listening to repetitive electronic music.

It has been often attributed to several famous figures in electronics. Usually it is said that Kristian Wilson, Nintendo's CEO, wrote it in 1989. But it is in fact Brigstocke's joke and he claims that:

(...) it is very unlikely that it was written by a Nintendo employee in 1989, being as Pac Man was still around and not much of a childhood memory (...)

Thursday, October 18, 2007

Use Wildcard Characters as Literal Characters (in LIKE comparisons)

We often use SQL queries with LIKE comparisons. When we do so, we usually use the % wildcard character. For instance, if i want to obtain every book with the word SQL in its title, in a Books database table, I would write something like:


You can also use the other wildcard characters/expressions: _ (underscore), [] and [^].

The problem comes when you need to find strings that contain these wildcard characters themselves. For instance, imagine you're searching a list of CD's and you want to find all CD's that contain the string [SOUNDTRACK]. As you can see you're searching a string that contains the wildcard characters [ and ].

You want those characters to be considered literal characters instead of wildcard characters, so you have enclose them in brackets, like so:


The ] character, for some reason, doesn't need to be enclosed in brackets but all other wildcard characters do: [, _ and %

So if you're going to run a LIKE comparison with a string that can contain wildcard characters and you want them to be considered like literal characters you can use the following trick (i'm using the soundtrack example):


SET @str = replace(@str, '[', '[[]')
SET @str = replace(@str, '_', '[_]')
SET @str = replace(@str, '%', '[%]')

SELECT * FROM CDs WHERE NAME LIKE '%' + @str + '%'

You can also use the ESCAPE clause. If you want to know more about LIKE comparisons, check here.

Friday, October 12, 2007

How to "clear screen" in javascript

I wanted to clear an HTML page after clicking a button. So how do I do it in javascript? I wanted something simple like the "cls" command that exists in several programming languages (including the "cls" command in the windows command prompt).

After a simple google search I found two options that I liked in the forum:




I prefer the second option because I can insert what I want in the innerHTML property.