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Re: Possible loop problems in database query

by davidrw (Prior)
on Apr 04, 2007 at 15:56 UTC ( #608308=note: print w/replies, xml ) Need Help??

in reply to Possible loop problems in database query

don't see the issue yet, but here's a crack at refactoring to simplify it some, which hopefully will lead you in the right direction..
recurQuery(0,0); my $cat_sth = $dbh->prepare("SELECT id, parentid, catname from categor +ies WHERE parentid = ?"); sub recurQuery { my ($parentId, $level) = @_; $cat_sth->execute($parentId) or die $dbh->errstr; while (my $data = $cat_sth->fetchrow_hashref) { printf qq{ <option name="%s">%s%s</option>\n }, $data->{catname}, '&nbsp;*' x $level, $data->{catname}, ; recurQuery( $data->{id}, $level+1 ); } }
Some notes:
  • prepare the statement once
  • use placeholders
  • the query only needs to be in the function once -- recursion does the rest; don't need to pre-test for rows .. the while loop just won't happen in the next level if there aren't any more children
  • the x operator can replace the for loop for the indenting
  • printf for cleaner output (also consider separating logic/presentation even further by having the recurQuery return an array, and loop over that to display later)
  • fetch hashref's instead of rows -- much easier to read a key name than just an array index
You should put in some protection for infinite recursion, too.

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