Nothing was printed out for @row1 by "print "@row1\n". In @IDnumber, only the last element of @row1 was printed out.

Sounds like normal behavior to me. When you are looping through you are overwriting @row1 with every iteration. In the last iteration you are overwriting it with an empty array. the variable falls out of scope and is therefore undefined. If you had use strict; turned on you might have caught that.

Here's some mods for ya!

my @IDnumber=();  #Initialize this...
while (my @row1 = $sth ->fetchrow_array){
    push @IDnumber,[@row1]; # save the row as an anon-array
    print "@row1\n";  #All the elements were printed out by this state
+ment.
        @IDnumber=@row1;
}
print "@row1\n";  #this is going to be empty! 
# snip! print  "@IDnumber\n";
foreach my $row(@IDnumber){
    printf "%s\n",join(",",@$row);
}
[download]

Try it.. you'll like it....

UPDATED: Didn't catch the scoping the first time through... Thanks Limbic~Region for watching my back!