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Re: MySQL count with DBI

by smitz (Chaplain)
on May 09, 2003 at 12:12 UTC ( [id://256835]=note: print w/replies, xml ) Need Help??

in reply to MySQL count with DBI

Yeah I HAD an idea, a combination Hat / Shoe garment, but the backers dropped out and I
lost EVERYTHING. Anyway, does this answer your non-question?
#!perl -w use strict; use DBI; my $dbh = DBI->connect('DBI:mysql:my_database', 'my_username', 'my_pas +sword') or die "Couldn't open database: $DBI::errstr; stopped"; # Prepare the SQL query for execution my $sth = $dbh->prepare(<<SQL) or die "Couldn't prepare statement: $DB +I::errstr; stopped"; SELECT COUNT(*) FROM music SQL # Execute the query $sth->execute() or die "Couldn't execute statement: $DBI::errstr; stop +ped"; #print result my ($count) = $sth->fetchrow_array(); print "Found $count results\n";

Yeah I copied and pasted from stephens excellent Reading from a database. Sorry, stephen

Replies are listed 'Best First'.
Re: Re: MySQL count with DBI
by Itatsumaki (Friar) on May 09, 2003 at 15:11 UTC

    Not to be a pita, but I think it is vastly clearer and safer to explicitly write SQLs explicitly into a variable, rather than read them from STDIN. In addition, I'm not a huge fan of using ->fetchrow_array() to get back a single method: that is exactly what ->selectrow_array() is meant for, I think. Finally, if the questioner is just starting to use DBI he should probably enable it's error-handling apparatus explicitly until he knows when/why he might not want to use it. Similarly, I would explicitly turn off autocommit to limit accidental damage to the DB.

    No major changes there, smitz, but just seems "safer" this way to me....

    my $dbh = DBI->connect('DBI:mysql:my_db', 'user', 'pass', {RaiseError +=> 1, PrintError => 1, AutoCommit => 0}) or die "Error connecting to +DB: $DBI::errstr\n"; my $sql = "SELECT COUNT(*) FROM music"; my @row = $dbh->selectrow_array($sql); print "Found $row[0] results\n";
      Yeah you are right, I should have been more discriminating when I copied stephen's tut, however, Im not sure why you say:
      > it is vastly clearer and safer to explicitly write SQLs explicitly into a variable, rather than read them from STDIN.
      Where is my snippet doing that?


        In fact you are not: I just skimmed your code too quickly and mis-read the <<SQL as <STDIN> for some reason. My bad.

        On the other hand, I *do* think it is much better to avoid allowing an application to receive a SQL statement as a parameter. That opens up lots of scope for problems, but you probably already knew that. :)

        Update in bold. Who knew one little word could make it mean the exact opposite of what I intended? :)

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