Eagle_f90 has asked for the wisdom of the Perl Monks concerning the following question:

I have now spent 2 hours looking over this code and testing different things and can not figure out what is wrong. Testing is showing that $OldRatting[0] is getting filled with the column name from the SQL command here: 
    $sth = $dbh -> prepare (qq~select ? from FanRatings where Title = 
+?~) or die $DBI::errstr;
    $sth -> execute ($rating, $filename) or die $DBI::errstr;
    @OldRating = $sth -> fetchrow_array;

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This is the full code I use. Can anyone tell me what I am doing wrong? 
#!/user/perl
use CGI q~:standard~;
use CGI::Cookie;
use CGI::Carp qw(fatalsToBrowser);
use strict;
use DBI;
my ($dbh, $sth, $filename, $rating, @current, @VotedOn, %cookies, $Can
+Vote, $value, $c, @OldRating, $result);
$filename = param('name');
$rating = param('rating');
%cookies = fetch CGI::Cookie;
$CanVote = 1;
if (exists($cookies{'FFInfoVotedOn'})) {
    @VotedOn = $cookies{'FFInfoVotedOn'} -> value;
    foreach $value (@VotedOn) {
        if ($value eq $filename) {
            $CanVote = 0;
        }
    }
}
$dbh = DBI -> connect ('dbi:ODBC:', '', '') or die $DBI::errstr;
if ($CanVote) {
    $result = 1;
    $sth = $dbh -> prepare (qq~select One, Two, Three, Four, Five from
+ FanRatings where Title = ?~) or die $DBI::errstr;
    $sth -> execute ($filename) or die $DBI::errstr;
    @current = $sth -> fetchrow_array;
    if (!defined $current[0]) {
        $sth = $dbh -> prepare (qq~insert FanRatings (Title, One, Two,
+ Three, Four, Five) values (?, 0, 0, 0, 0, 0)~) or die $DBI::errstr;
        $sth -> execute ($filename) or die $DBI::errstr;
    }
    $sth = $dbh -> prepare (qq~select ? from FanRatings where Title = 
+?~) or die $DBI::errstr;
    $sth -> execute ($rating, $filename) or die $DBI::errstr;
    @OldRating = $sth -> fetchrow_array;
    $OldRating[0]++;
    $sth = $dbh -> prepare (qq~update FanRatings set ? = ? where Title
+ = ?~) or die $DBI::errstr;
    $sth -> execute ($rating, $OldRating[0], $filename) or die $DBI::e
+rrstr;
    @VotedOn = (@VotedOn, $filename);
    $c = new CGI::Cookie(-name => 'FFInfoVotedOn',
                         -value => "@VotedOn",
                         -expires => '+10Y',
                         );
}
$dbh -> disconnect;

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Replies are listed 'Best First'.
Re: Variable is filled with column name not data, can't figure out why.
by grep (Monsignor) on Jul 17, 2007 at 03:20 UTC
    Straight from the DBI Docs: 
    With most drivers, placeholders can't be used for any element of 
a statement that would prevent the database server from validating 
the statement and creating a query execution plan for it. 
For example:

  "SELECT name, age FROM ?"         # wrong (will probably fail)
  "SELECT name, ?   FROM people"    # wrong (but may not 'fail')

    [download]

    So you'll need to change your code to: 

    $sth = $dbh->prepare(qq~select $rating from FanRatings where Title = ?
+~) or die $DBI::errstr;
$sth->execute($filename) or die $DBI::errstr;

    [download]

    grep

[reply]
[d/l]
[select]
      Now that you point that out I remember reading it last week when learning about the place holders. It just never poped back to me as the problem. Thanks for the help!
[reply]

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