Mysql query result manipulation

Not sure if this belongs here but...

I'm working away on a bit of a website when a technical question hit me on the head, and since I'm way away from looking at the application of the solution, I thought I'd find out if the solution was even possible (to save myself some lost time).

There will be a couple of different menus on this site, each with its own sections to be displayed in them. When I run a query and the set of sections are returned, can I transfer from the returned "recordset" (I know thats asp jargon, but I dont know the php/mysql equivalent [yet]) some of the results into another "recordset" (or array) and then manipulate the new recordset knowing that I only have a subset of the original returned recordset in either location (not very good at explaining am I).

For example:
[php]
sectionlist = mysql_query("select * from section;")
[/php]

will return the complete section list into the sectionlist variable, can I then Do something like this:
[php]
for(i = 0; i < sectionlist.length; i++)
{
if sectionlist.menuid ==1
{
subset = subset + sectionlist;
delete(sectionlist)
}
}
[/php]

Hope thats clearer.

Now I'm assuming I can build the second array (obviously not with that code [yes I know its bs code, so you don't need to correct it]) because it seems like a logical thing to be able to do, but can I manipulate the original array to delete each item as I add it to the new array??

Just a simple overview is all I want, if its possible I'll investigate how, if not then you might be able to save me some time.

Thanks in advance for any help.

Baz_