Re: Programming Question

[ CC to Author ]

On Oct 4, 2005, at 10:37 AM, Douglas S. Davis wrote:

> My problem (and I am sure it must be simple to do) is that I can't  
> figure out how to compare the list of possible numbers (100 - 499)  
> with the list of already in use numbers returned by my query.  I've  
> tried various loops and while statements all to no avail.  Usually  
> what I get is that for *each* number in the result set of my query, it  
> prints out all of the numbers from 100 - 499.
>
> Can anyone point me in the right direction.    So in other words, when  
> I do my fetchrow() on the MySQL table, how can I take the results and  
> compare them to the 100 - 499 set of numbers.
>

My suggestion - don't fetch each row, unless there is a compelling  
reason. Fetch all of the matching rows at once as a hashref. For  
instance, if you have a table called tblcourses with the following  
structure:

courseNumber | courseTitle | departmentNumber | creditHours |  
instructor |
------------------------------------------------------------------------ 
--

# UNTESTED
my $keyfield = 'courseNumber';

my $courses = $dbh->selectall_hashref( q(Select * From tblcourses Where  
departmentNumber = ?), $keyfield, $departmentNumber );

foreach ( 100..499 ) {
	# if $courses -> { $_ } is defined, the class exists
	next if $courses -> { $_ };
	
	# If not do something with the unassigned course number in $_
}

$courses has a structure like:

$courses = {
			'100' => {
						'courseTitle' => 'Introduction to Programming',
						'courseNumber' => '100',
						'departmentNumber => '10',
						'creditHours'	=> '3.0',
						'instructor => 'Douglas S. Davis'
					},	
			....
		};

						


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