Question

Have some Perl code which is using the DBI module – (the code is at work, I can post it in the morning if needed) – but mainly trying to get a sense of what DBI needs to do an update to a row — and get either errors back, or confirmation that the UPDATE was executed.

(Below is just a basic example, feel free to give your own example and sample DDL if you want… just want some code that I know works. I’ve run my code via the Perl PtkDB debugger, and can “see” the SQL it generating and executing — even paste in in the MySQL consol and execute it… but it’s doing nothing in the Perl, even thought the select statements are working. Mainly just want a better idea of how DBI is handling UPDATE to MySQL, and if there’s any built in feature in DBI that would make debugging this more simple. Thanks!)

So, please supply one full Perl script that:

• Sets the connection (MySQL)
• SELECT row two based on ID and get the first and last name
• Lowercase the names
• UPDATE the table
• disconnect

Sample TABLE

<COL01>Id <COL02>FirstName <COL03>LastName
<ROW01-COL01>1 <ROW01-COL02>John <ROW01-COL03>Smith
<ROW02-COL01>2 <ROW02-COL02>Jane <ROW02-COL03>Doe

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UPDATE (1): Code in question is below. The ONLY thing I’ve changed is remove code not related to the issue and the config info (eg database name, user, password, etc.) and made the value production for the variables super simple. This code was created by someone else and in a legacy code base.

use strict;
use warnings;
use DBI;

sub dbOpen {
    my $dsn; 
    my $dbh;
    $dsn = "DBI:mysql:database=databasename;host=localhost;port=3306";
    $dbh = DBI->connect( $dsn, "root", "password" ) ||
    print STDERR "FATAL: Could not connect to database.\n$DBI::errstr\n";
    $dbh->{ AutoCommit } = 0;
    return($dbh);
} # END sub dbOpen

my $Data;
$Data = &dbOpen();

my ($sql,$rs,$sql_update_result);
my $column2,
my $column3;
my $id;
$column2 = 2,
$column3 = 3;
$id = 1;

$sql = "UPDATE table SET column1 = NULL, column2 = ".$column2.", column3 = ".$column3." WHERE id = ".$id.";";
$rs = $Data->prepare( $sql );
$rs->execute() || &die_clean("Couldn't execute\n$sql\n".$Data->errstr."\n" );
($sql_update_result) = $rs->fetchrow;

$Data->disconnect();

DDL for MySQL — if needed, just comment and I’ll post one.

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UPDATE (2):

Final found one complete example, though it’s only for a select statement and not even inserting any VARs into the SQL: http://search.cpan.org/~timb/DBI/DBI.pm#Simple_Examples

Answer 1

Almost copy and paste from DBI Synopsis:

use DBI;
$dbh = DBI->connect($data_source, $username, $auth, \%attr);
$statement = "UPDATE some_table SET som_col = ? WHERE id = ?";
$rv  = $dbh->do($statement, undef, $som_val, $id); 
$DBI::err && die $DBI::errstr;
$rc  = $dbh->disconnect;