ok, if you are like me, i used to send two queries when i need to find out an associated field with another one. for example, lets say i have a wallpaper site and i have a category and the wallpaper. now each wallpaper will have to be organized into each parent category. like this for example:

Categories:
Animals (CatId=1)
- Lions
- Bears
- Dogs

Cars (CatId=2)
- Ferrari
- Ford
- Nissan
- Chevy
- Toyota

as you can see from my example above, i have two categories, one is Animals, which the CatId=1 and the other one is Cars which has a CatId=2 . and each categories has its wallpapers.

now lets say the user is in the Lions page, but i want to also get the Lions Category in this case, Animals. that way i can say
This Lion Wallpaper is Found in the Animals Category

ok, so you will understan what im talking about here lets say the url page i am on is:
http://www.wallpaperama.com/page.php?CatId=2

this is how my sql query will look like:
$sql ="SELECT c.CatName, w.WallpaperName FROM CategoryTable c, WallpaperTable w WHERE CatId = $_GET[CatId]";


now with this, i can get the values from two different tables in one shot using this php mysql code.

i hope with this script you can learn something new, this way you can avoid sending two queries, because the less queries you do, the better