Listing 8: Insert-New-Person-2.pl, Using eval to Trap Errors
#!/usr/bin/perl -wT
# insert-new-person-2.pl
use strict;
use DBI;
# Get parameters
my ($new_name, $new_email, $monthly_gross) = @ARGV;
die qw { "You need to specify (a) name
(b) e-mail address, (c) monthly gross"
} unless (@ARGV == 3);
# Connect to the PostgreSQL server with DBD::Pg
my $host = 'ahad-haam';
my $user = 'reuven';
my $password = '';
my $dsn = "DBI:Pg:dbname=test;host=$host;";
my $dbh =
DBI->connect($dsn, $user, $password,
{RaiseError => 1, AutoCommit => 0});
eval {
# Insert the new employee into the People table
my $sql = "INSERT INTO People ";
$sql .= " (name, email) ";
$sql .= "VALUES ";
$sql .= " (?, ?) ";
$dbh->do($sql, undef, $new_name, $new_email);
# Get the person_id that we just inserted
$sql = "SELECT currval('people_person ";
$sql = "_id_seq')";
my $person_id = $dbh->selectrow_array($sql);
# Now insert a row into the Salaries table, using $person_id
$sql = "INSERT INTO Salaries ";
$sql .= " (person_id, monthly_gross, as_of, ";
$sql .= " approved_by, notes) ";
$sql .= "VALUES ";
$sql .= " (?, ?, NOW(), ?, ?) ";
# We will assume here that the boss has a
# person_id of 1 -- but
# hard-wiring this sort of information is a
# bad idea in practice.
$dbh->do($sql, undef, $person_id, $monthly_gross,
1, "Testing insert");
# If we do not commit this transaction,
# PostgreSQL will behave as
# if we rolled it back and it never happened!
$dbh->commit();
};
# If the eval died in the middle, then $@ was set.
# We can now perform
# a rollback, as well as give the user a message.
if ($@)
{
print "Sorry, but the transaction failed.
Better luck next time!\n";
$dbh->rollback();
}
$dbh->disconnect;
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