Re: Display row number perl DBI

Always use strict; use warnings; at the beginning of your perl code. It catches common mistakes, including the one you are making.

The problem is that Perl replaces variable names in double-quoted strings by their value (we call that "interpolation"), and @rownum happens to look like a variable name in Perl. So use single-quote strings instead:

$sth = $dbh->prepare('Select @rownum:=@rownum+1 rank, p.* from player 
+p, (SELECT @rownum:=0) r order by score desc limit 10');
[download]

Perl 6 - the future is here, just unevenly distributed

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Re^2: Display row number perl DBI by romy_mathew (Beadle) on May 28, 2012 at 17:50 UTC
Hi Thanks that worked ...but what if I need to use a variable in limit e.g my $temp = 50; $sth = $dbh->prepare('Select @rownum:=@rownum+1 rank, p.* from player +p, (SELECT @rownum:=0) r order by score desc limit $temp');	[reply]
Re^3: Display row number perl DBI by moritz (Cardinal) on May 28, 2012 at 18:13 UTC
You use placeholders: `$sth = $dbh->prepare('Select @rownum:=@rownum+1 rank, p.* from player ++p, (SELECT @rownum:=0) r order by score desc limit ?'); # and later $sth->execute($temp);` [download] This is generally safer than interpolating variables into SQL strings, and prevents SQL injection attacks. See also: DBI, and perlop for the rules about string interpolation and escaping. Perl 6 - the future is here, just unevenly distributed	[reply] [d/l]
Re^3: Display row number perl DBI by vinian (Beadle) on May 29, 2012 at 08:45 UTC
you can also use backslash `$sth = $dbh->prepare("Select \@rownum:=\@rownum+1 rank, p.* from playe +r +p, (SELECT \@rownum:=0) r order by score desc limit $temp");` [download] but it looks a little oddly	[reply] [d/l]