Dear Shmuel,
Yes, I am well aware that I am using Perl’s ‘eval’! And no, $dbh->do() cannot
be used to retrieve data.
But I had my share of the RTFM syndrom L. The very first line of the ‘eval’
page in perldoc is:
In the first form, the return value of EXPR is parsed and executed as if it
were a little Perl program.
(my enhancement.) So I changed case #1 to be:
my $raw_string_1 = '{return "WHERE col = \'$sql_date\'"}';
That when eval’ed, yielded:
WHERE col = '2014-7-31'
As required.
Sorry folks to bother you
Meir
From: Perl [mailto:[email protected]] On Behalf Of Shmuel Fomberg
Sent: יום ה 31 יולי 2014 18:22
To: Perl in Israel
Subject: Re: [Israel.pm] Not understood behavior of 'eval'
Hi Meir.
I think that you are confusing perl's eval and DBI eval.
Your code is using perl's eval,
which is invalid for #1, (so you get undef and can check $@ for error string)
and for #2, the evaluated string is $sql_date, so you get the date inside it.
if you want to have SQL command to the DB, check the DBI module:
https://metacpan.org/pod/DBI
I think you are looking for the 'do' command.
Shmuel.
On Fri, Aug 1, 2014 at 12:15 AM, Meir Guttman <[email protected]> wrote:
Please Perlers,
The following script:
<code>
use strict;
use warnings;
my $sql_date = '2014-7-31';
my $raw_string_1 = 'WHERE col = $sql_date';
my $raw_string_2 = '$sql_date';
my $evaled_1 = eval $raw_string_1; # yields 'undef'
my $evaled_2 = eval $raw_string_2; # yields '2014-7-31'
print "First: $evaled_1\nSecond: $evaled_2\n";
</code>
Yields 'undef' (and a concatenation warning) for $evaled_1 and '2014-7-31'
for $evaled_2. Why???
Notes:
1) I need the first form to work.
2) I am well aware of the DBI/DBD 'prepare()' with place holders. Mine is
not the case for it, since 'col' is a run-time column name and so it cannot
be assigned a place holder.
3) Neither can the date be assigned to a place holder. It is not always a
date. The "WHERE" clause is an arbitrary complex compilation read from an
INI file and various parts in it must be substituted by Perl variables
values, also only determined at run-time.
Thanks!
Meir
_______________________________________________
Perl mailing list
[email protected]
http://mail.perl.org.il/mailman/listinfo/perl
_______________________________________________
Perl mailing list
[email protected]
http://mail.perl.org.il/mailman/listinfo/perl
