Creating strings with specified names

pc0019 has asked for the wisdom of the Perl Monks concerning the following question:

## get a list of the field names
my $keys = join (', ', @keys);
## get number of placeholders required (number of field names)
my $placeholder_count = @data;
## make $placeholder_count number of ?'s with a comma after each
my $placeholders = '?, ' x $placeholder_count;
## remove last space and comma
$placeholders = substr($placeholders, 0, - 2);
## make a string containing each piece of data separated by commas
my $data = '"' . join('", "', @data) . '"';

my $dbh = DBI->connect("DBI:mysql:database=$database;host=localhost", 
+$username, $password, {'RaiseError' => 1});
my $sth = $dbh->prepare("INSERT INTO $table ($keys) VALUES ($placehold
+ers)") or die $dbh->errstr;
$sth->execute($data) or die $dbh->errstr;
[download]

I am making a script which sends data to a MySQL database. From the code above, the penultimate line would read something like this:

my $sth = $dbh->prepare( "INSERT INTO table01 (field1, field2, field3) VALUES (?, ?, ?)" ) or die $dbh->errstr;

And on the last line, $data = '"rise", "against", "ftw"'. The problem is, I get the message:

DBD::mysql::st execute failed: called with 1 bind variables when 3 are needed

Perl is seeing my $data at $sth->execute($data) as one variable, not a list. So how could I create the variables there?

I guess there are other ways to do this, but I would like to know how to create variables within Perl with specific names anyway - getting a language to write its own code is awesome :D

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Re: Creating strings with specified names by kyle (Abbot) on Aug 05, 2008 at 21:51 UTC
`$sth->execute(@data) or die $dbh->errstr;` [download] You don't have to put quotes around the elements of `@data` when you use placeholders—DBI does that for you.	[reply] [d/l] [select]
Re^2: Creating strings with specified names by pc0019 (Acolyte) on Aug 07, 2008 at 20:52 UTC
Oops, should have thought of that. Thanks! Is what I suggested possible?	[reply]
Re^3: Creating strings with specified names by kyle (Abbot) on Aug 07, 2008 at 21:14 UTC
Writing Perl that creates variables with a name specified at run time is pretty easy, but it's generally not a good idea. `$name = 'foo'; $$name = 'bar'; print "foo = $foo\n"; __END__ foo = bar` [download] Note that doesn't work if you use strict (which is always a good idea). In that case, you wind up with something like this: `my $name = 'foo'; { no strict 'refs'; $$name = 'bar'; } print "foo = $main::foo\n";` [download] See how I still had to use the explicit package name to refer to the variable for printing. You can do a lot with eval too.	[reply] [d/l] [select]
Re: Creating strings with specified names by chromatic (Archbishop) on Aug 05, 2008 at 23:34 UTC
Perl is seeing my `$data` at `$sth->execute($data)` as one variable, not a list. That's because `$data` is a scalar, not a list. join creates a string from a list.	[reply] [d/l] [select]