sub table_exists {
    my $db = shift;
    my $table = shift;
    my @tables = $db->tables('','','','TABLE');
    if (@tables) {
        for (@tables) {
            next unless $_;
            return 1 if $_ eq $table
        }
    }
    else {
        eval {
            local $db->{PrintError} = 0;
            local $db->{RaiseError} = 1;
            $db->do(qq{SELECT * FROM $table WHERE 1 = 0 });
        };
        return 1 unless $@;
    }
    return 0;
}

if (table_exists( $dbh, "employees") {
    print "it's there!\n";
}
else {
    print "table not found!\n";
    $dbh->do( $create_query );
}

##</code><code>##

    my $create_query = qq{
        create table employees (
            id int not null primary key,
            name char(20) not null,
            salary int
        )
    };
    $dbh->do($create_query);
    my @fields = (qw(id name salary));
    my $fieldlist = join ", ", @fields;
    my $field_placeholders = join ", ", map {'?'} @fields;


##</code><code>##

    my $insert_query = qq{
        INSERT INTO employees ( $fieldlist )
         VALUES ( $field_placeholders )};
    my $sth= $dbh->prepare( $insert_query );
# $insert_query = "INSERT INTO employees ( id, name, salary )
#            VALUES ( ?, ?, ? )";

##</code><code>##

    my ($id,  $name, $salary)  = (5, 'Sal', 4500);
    $sth->execute($id, $name, $salary);

##</code><code>##

    while ( get_values($id, $name, $salary) {
        $sth->execute($id, $name, $salary);
    }

##</code><code>##

    my @employees_lol = (
        [1, 'Fred',   5000],
        [2, 'Joshua', 5000]
    );
    for (@employees_lol) {
        $sth->execute(@$_);
    }

##</code><code>##

    my @employees_loh = (
        {id => 3, name => 'Kim',  salary =>  5600},
        {id => 4, name => 'Dave', salary =>  6000},
    );
    for (@employees_loh) {
        $sth->execute($_->{id}, $_->{name}, $_->{salary});
    }

##</code><code>##

    for (@employees_loh) {
        $sth->execute(@{$_}{@fields})
    }

##</code><code>##

    my $query1 = qq{select name from employees};
    my $sth= $dbh->prepare($query1);
    $sth->execute;
    my @names =();
    while (my ($name) = $sth->fetchrow_array) {
        push @names, $name;
    }

##</code><code>##

    my $query2 = qq{select id, name, salary from employees};
    my @names = map {$_->[1]}
        @{$dbh->selectall_arrayref($query2)};
__END__
@names = (qw(Fred Joshua Kim Dave Sal));

##</code><code>##

    #
    # either
    #
    my $names_ref = $dbh->selectcol_arrayref($query1);
    #
    # or
    #
    my @names = @{$dbh->selectcol_arrayref($query1)};
__END__
$names_ref = ['Fred', 'Joshua', 'Kim', 'Dave', 'Sal'];
@names = ('Fred', 'Joshua', 'Kim', 'Dave', 'Sal');

##</code><code>##

    my $sth = $dbh->prepare($query2);
    $sth->execute();
    my @names = map {$_->[1]}
        @{$sth->fetchall_arrayref([0,-2])};
__END__
@names = (qw(Fred Joshua Kim Dave Sal));

##</code><code>##

    #
    # either
    #
    my $employees_lol = $dbh->selectall_arrayref($query2);

    #
    # or
    #
    my $sth = $dbh->prepare($query2);
    $sth->execute();
    my $employees_lol = $sth->fetchall_arrayref();
__END__
$employees_lol = [
  [ '1', 'Fred', '5000' ],
  [ '2', 'Joshua', '5000' ],
  [ '3', 'Kim', '5600' ],
  [ '4', 'Dave', '6000' ],
  [ '5', 'Sal', '4500' ]
];

##</code><code>##

    my $sth = $dbh->prepare($query2);
    $sth->execute();
    my $employees_loh = $sth->fetchall_arrayref({});
__END__
$employees_loh = [
  { 'salary' => '5000', 'id' => '1', 'name' => 'Fred' },
  { 'salary' => '5000', 'id' => '2', 'name' => 'Joshua' },
  { 'salary' => '5600', 'id' => '3', 'name' => 'Kim' },
  { 'salary' => '6000', 'id' => '4', 'name' => 'Dave' },
  { 'salary' => '4500', 'id' => '5', 'name' => 'Sal' }
];

##</code><code>##

    my $employees_loh = $dbh->selectall_arrayref($query2, {Slice => {}});

##</code><code>##

    my $sth = $dbh->prepare($query2);
    $sth->execute();
    my $employees_partial_loh =
        $sth->fetchall_arrayref({name =>1, salary=>1});
__END__
$employees_partial_loh = [
  { 'salary' => '5000', 'name' => 'Fred' },
  { 'salary' => '5000', 'name' => 'Joshua' },
  { 'salary' => '5600', 'name' => 'Kim' },
  { 'salary' => '6000', 'name' => 'Dave' },

  { 'salary' => '4500', 'name' => 'Sal' }
];

##</code><code>##

    my %employees_h =
        map { $_->[1], $_->[2]}
        @{$dbh->selectall_arrayref($query2)};
__END__
%employees_h = (
    'Fred' => '5000' ,
    'Joshua' => '5000' ,
    'Kim' => '5600' ,
    'Dave' => '6000' ,
    'Sal' => '4500'
    );

##</code><code>##

    #
    # either
    #
    my %employees_h2 =
        map { $_->[0], [ $_->[1], $_->[2] ]}
        @{$dbh->selectall_arrayref($query2)};
    #
    # or
    #
    my %employees_h2 =
        map { shift @$_, [ @$_ ]}
        @{$dbh->selectall_arrayref($query2)};
__END__
%employees_h2 = (
  '1' => [ 'Fred', '5000' ],
  '2' => [ 'Joshua', '5000' ],
  '3' => [ 'Kim', '5600' ],
  '4' => [ 'Dave', '6000' ],
  '5' => [ 'Sal', '4500' ]
);

##</code><code>##

    my $employees_hoh = $dbh->selectall_hashref($query2, 1);
__END__
$employees_hoh = {
 '1' => { 'salary' => '5000', 'id' => '1', 'name' => 'Fred' },
 '2' => { 'salary' => '5000', 'id' => '2', 'name' => 'Joshua' },
 '3' => { 'salary' => '5600', 'id' => '3', 'name' => 'Kim' },
 '4' => { 'salary' => '6000', 'id' => '4', 'name' => 'Dave' },
 '5' => { 'salary' => '4500', 'id' => '5', 'name' => 'Sal' }
};

##</code><code>##

    my $employees_hoh2 = $dbh->selectall_hashref($query2, 3);
__END__
$employees_hoh2 = {
  '5000' => { 'salary' => '5000', 'id' => '2', 'name' => 'Joshua' },
  '5600' => { 'salary' => '5600', 'id' => '3', 'name' => 'Kim' },
  '4500' => { 'salary' => '4500', 'id' => '5', 'name' => 'Sal' },
  '6000' => { 'salary' => '6000', 'id' => '4', 'name' => 'Dave' }
 };

##</code><code>##

    my ($id, $name, $salary) ;

    $sth = $dbh->prepare($query2);
    $sth->execute;

    $sth->bind_col(1, \$id);
    $sth->bind_col(2, \$name);
    $sth->bind_col(3, \$salary);

    print "$id\t$name\t$salary\n" while $sth->fetchrow_arrayref;
__END__
1       Fred    5000
2       Joshua  5000
3       Kim         5600
4       Dave    6000
5       Sal         4500

##</code><code>##

    $sth->execute;

    #
    # either
    #
    $sth->bind_columns ( \$id, \$name, \$salary );

    #
    # or
    #
    $sth->bind_columns ( \( $id, $name, $salary ) );

    print "$id\t$name\t$salary\n" while $sth->fetchrow_arrayref;

##</code><code>##

    my @empl = (undef, undef, undef);
    $sth->execute;
     
    #
    # either
    #
    $sth->bind_columns( map {\$_} @empl );

    #
    # or (perhaps better)
    #
    $sth->bind_columns ( \( @empl ) );    

    print join( "\t", @empl), $/ while $sth->fetchrow_arrayref;

##</code><code>##

    @empl = ( \$id, \$name, \$salary );
    $sth->execute;

    $sth->bind_columns( @empl );
    print "$id\t$name\t$salary\n" while $sth->fetch;

##</code><code>##

    my %rec = (
        emp_id => undef,
        first_name => undef,
        monthly_payment => undef
    );

    $sth->execute;

    $sth->bind_col(1, \$rec{emp_id});
    $sth->bind_col(2, \$rec{first_name});
    $sth->bind_col(3, \$rec{monthly_payment});
    print "$rec{emp_id}\t",
          "$rec{first_name}\t",
          "$rec{monthly_payment}\n"
                while $sth->fetchrow_arrayref;

##</code><code>##

    my @fields = (qw(emp_id first_name monthly_payment));

    $sth->execute;
    my %rec =();

    $sth->bind_columns(map {\$rec{$_}} @fields);

    print "$rec{emp_id}\t",
          "$rec{first_name}\t",
          "$rec{monthly_payment}\n"
        while $sth->fetchrow_arrayref;

##</code><code>##


    use Benchmark (qw(cmpthese));

    $sth = $dbh->prepare($query2);

    cmpthese (50000, { # adjust this to the speed of your machine
    fr_hashref => sub {
        $sth->execute;
        while (my $hash = $sth->fetchrow_hashref) { }
    },
    fr_arrayref => sub {
        $sth->execute;
        while (my $aref = $sth->fetchrow_arrayref) { }
    },
    man_hashref=> sub{
        my %hash = (id =>undef, name => undef, salary => undef);
        $sth->execute;
        $sth->bind_columns( \$hash{id},
                \$hash{name}, \$hash{salary});
        while ($sth->fetchrow_arrayref) { }
    }
    });
__END__

(output edited for display purposes)
Benchmark: timing 50000 iterations of
    fr_arrayref, fr_hashref, man_hashref...

fr_arrayref:  5 wallclock secs ( 4.68 usr +  0.63 sys =  5.31 CPU)
fr_hashref:  13 wallclock secs (12.13 usr +  0.83 sys = 12.96 CPU)
man_hashref:  6 wallclock secs ( 5.08 usr +  0.68 sys =  5.76 CPU)

            Rate  fr_hashref    man_hashref fr_arrayref
fr_hashref  3858/s        --           -56%        -59%
man_hashref 8681/s      125%             --         -8%
fr_arrayref 9416/s      144%             8%          --

##</code><code>##

    $sth = $dbh->prepare(qq{
        SELECT
            a.id, b.id
        FROM
            employees a
            INNER JOIN employees b ON (a.id=b.id)
        WHERE a.id = 1
        });
    $sth->execute;
    print "using a hashref\n";
    while (my $hashref = $sth->fetchrow_hashref) {
        for (keys %$hashref) {
            print "$_ => $hashref->{$_}\t"
        }
        print $/;
    }
    #
    # using a hashref
    # id => 1
    #

    $sth->execute;
    print "using a arrayref\n";
    print "columns => ",join( ",", @{$sth->{NAME}}), $/;
    while (my $aref = $sth->fetchrow_arrayref) {
        print "@$aref\n";
    }
    #
    # using a arrayref
    # columns => id,id
    # 1 1