I had previously asked a question regarding testing for a numeric or string value. That thread ended up discussing placeholders to eliminate the need for the test. So I tried using placeholder after reading through the links provided and could not find a solution.

Here's what I currently have (that works) but I would like to better understand how placeholders could simplify the code. This is used to create a backup for a mySQL database (Part of a mySQL table editor) 

# 1.  Download text-only data. Comma delimited and quoted strings for 
+?easy? upload.
my $table = $q->param('dbtable'); # Can be any table in the database
my @field_type = ();
my $n = 0;  
my $sth = $dbh->prepare("DESCRIBE $table");  $sth->execute();
while (my @field_descr = $sth->fetchrow_array) {
    @field_type[$n] = ($field_descr[1] =~ /char/i) ? 1 : 0;  # Set to 
+1 if string
    $n++;
}
$sth->finish();
$sth = $dbh->prepare("SELECT * FROM $table");  $sth->execute();
print "Content-Type: text/plain\n\n";
while (my @record = $sth->fetchrow_array()) {
    # Build a string of each record, comma delimited, and inserting qu
+otes as needed
    my ($recStr,$dl,$n) = ("","",0);
    foreach my $field (@record) {
        $field =~ s/(\n|\r)//g; # Get rid of any return chars that MAY
+ have been erroneously uploaded.
        $recStr .= ($field_type[$n]) ? "$dl'$field'" : "$dl$field"; # 
+Insert the quotes.
        $dl = ",";  $n++;
    }
    print "$recStr\n";
}
$sth->finish();

# 2. Upload the data.
my $dbdata = $q->param('dbdata');
my @filedata = <$dbdata>;
foreach my $record (@filedata) {
    my $sql = "INSERT INTO $table VALUES ($record)";
    my $rows = $dbh->do($sql);
}

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If I could eliminate the need for the quotes, it would greatly simplify the 'download' code. I understand that, if I knew the number of fields in the table, I could use placeholders to add the quotes; but I don't because it can be any table in the database. 
my $sql = "INSERT INTO tablename VALUES(?,?,?,?)";
my $sth = $dbh->prepare($sql);
foreach my $record (@filedata) {
    $sth->execute($fa,$fb,$fc,$fd);
}

[download]
Any ideas, thoughts, or comments would be appreciated and will, hopefully :), expand my limited Perl knowledge

In reply to Understanding placeholders by Anonymous Monk

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