That would not be true.
You'd receive a message stating that you had one placeholder, but you
were passing 3 arugments, and it script would die on the error.
havoc
ryc wrote:
>
> I was not aware of placeholders, and the benifits of using them instead of
> using $dbh->quote(). It doesnt make sence that the DBI version of quote isnt
> as thorough as having the code behind placeholding do it. But anyhow, I have
> a few questions as to how this works. Here is an example from the Perl
> DBH::mysql docs:
>
> my @names = ['Flaherty', 'Jones', 'Smith'];
> my $sth = $dbh->prepare("UPDATE contact
> SET phone = '555-1212'
> WHERE last_name = ?");
> $sth->execute(@names);
> $sth->finish;
>
> So most likely this query will return 3 rows, each corresponding to the last
> names contained in the array. Does this mean you can not use more than one
> place holder per query? What if the 'WHERE' statement was "WHERE last_name =
> ? AND first_name = ?". So you do an execute like this:
> $sth->execute(@lnames,@fnames) ... This would not work because as far as the
> execute function is concerned, these two arrays are the same (if you want to
> pass them as seperate arguments you must pass references rather than the
> object itself). Anyhow one how placeholders for multiple variables can be
> used? Thanks.
>
> ryan
>
> > r> Seems that you are not taking advantage of Perl. This is what you can
> do:
> >
> > No, he is taking advantage of placeholders. It is much better to use
> > placeholder for value substitution that substitute values directly
> > into query with Perl because there is no need to escape values (do you
> > know that $dbh->quote doesn't quote reliably?) and $sth can be reused
> > for simular queries (which can give perfomance gain on some SQL
> > databases).
> >
> > However usually placeholders can be used only for value
> > substitutuion. 'DESC' cannot be substituted since it is a part of
> > query.
> >
> > r> $parentid = x;
> > r> $orderby = 'DESC';
> > r> my $sth = $dbh -> prepare (qq{
> > r> SELECT message.name, contents, user.name, message.id
> > r> FROM message, user
> > r> WHERE folder='N' and parentid=$parentid
> > r> GROUP BY message.id
> > r> ORDER BY time $orderby
> > r> }) || die $dbh->errstr;
> >
> > r> You can put any variable inside the string... Note that I changed the
> q{
> > r> ... } to qq{ ... }
> >
> > r> $string = q{ string } is the same as $string = 'string';
> > r> $string = qq{ string } is the same as $string = "string";
> >
> > r> Note that variables inside of strings enclosed by '' will not be
> translated,
> > r> only strings enclosed by "" (or qq{} =) ).
> >
> > --
> > -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
> > | Ilya Martynov (http://martynov.org/)
> |
> > | GnuPG 1024D/323BDEE6 D7F7 561E 4C1D 8A15 8E80 E4AE BE1A 53EB 323B DEE6
> |
> > | AGAVA Software Company (http://www.agava.com/)
> |
> > -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
> >
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