Make this the fourth SOPW on this problem, hoping this will be the last :) In short, I have a MySQL database that has infinite levels of categories/subcategories. It's set up like.. 
id   parentid   catname   catdesk

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Using the parentid to locate the next-up category to which it belongs. If it's 0, it's a parent category. I wrote the hack below but it seemingly goes through a loop and reprints the subcategories many times. 
# print the beginning of the select
print "<select name='categories' SIZE='5'>\n";

# select top-level elements, and specify top level
recurQuery(0,0);

# my super recurse the tree function, takes 2 options being parentid, 
+and current level
sub recurQuery {
        my $parentId=$_[0];
        my $level=$_[1];
        my $data = "SELECT id, parentid, catname from categories WHERE
+ parentid = $parentId";
        my $sth = $dbh->prepare($data);
        $sth->execute() or die $dbh->errstr;

        # loop through results
        while (my @results = $sth->fetchrow_array) {
                
                # print the beginning of the option box
                print"<option name='$results[2]'>";
                
                # loop based on level, for indentation
                for (my $i = 0; $i < $level; $i++) {
                        print "&nbsp;*";
                }
                
                # print end of option box
                print $results[2]."</option>\n";
                
                # find child elements of this one
                my $data = "SELECT id, parentid, catname from categori
+es WHERE parentid = $results[0]";
                my $sth = $dbh->prepare($data);
                $sth->execute() or $dbh->errstr;
                
                # get number of rows returned
                my $rownumbersub = $sth->rows;
                
                # if rows returned, exec this
                if($rownumbersub > 0) {
                        
                        # loop through children
                        while (my @resultssub = $sth->fetchrow_array) 
+{
                                
                                # re-exec this function with the child
+ ID and new level
                                recurQuery($resultssub[1],$level+1);
                        }
                }
        }
}

# close that thar select box

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The results are as follows. As you can see, the subcategories reprint themselves. They are only in the database ONE time, so that can't be the problem. Can anyone see what might be going on her? 
<select name='categories' SIZE='5'>
<option name='insect'>insect</option>

<option name='mammal'>mammal</option>
<option name='Sea Life'>&nbsp;*Sea Life</option>
<option name='Dolphin'>&nbsp;*&nbsp;*Dolphin</option>
<option name='Seal'>&nbsp;*&nbsp;*Seal</option>
<option name='Dolphin'>&nbsp;*&nbsp;*Dolphin</option>
<option name='Seal'>&nbsp;*&nbsp;*Seal</option>
<option name='Cats'>&nbsp;*Cats</option>

<option name='Dogs'>&nbsp;*Dogs</option>
<option name='Sea Life'>&nbsp;*Sea Life</option>
<option name='Dolphin'>&nbsp;*&nbsp;*Dolphin</option>
<option name='Seal'>&nbsp;*&nbsp;*Seal</option>
<option name='Dolphin'>&nbsp;*&nbsp;*Dolphin</option>
<option name='Seal'>&nbsp;*&nbsp;*Seal</option>
<option name='Cats'>&nbsp;*Cats</option>

<option name='Dogs'>&nbsp;*Dogs</option>
<option name='Sea Life'>&nbsp;*Sea Life</option>
<option name='Dolphin'>&nbsp;*&nbsp;*Dolphin</option>
<option name='Seal'>&nbsp;*&nbsp;*Seal</option>
<option name='Dolphin'>&nbsp;*&nbsp;*Dolphin</option>
<option name='Seal'>&nbsp;*&nbsp;*Seal</option>
<option name='Cats'>&nbsp;*Cats</option>

<option name='Dogs'>&nbsp;*Dogs</option>
<option name='bird'>bird</option>
</select>

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In reply to Possible loop problems in database query by coldfingertips

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