sub get_table_CRC {

    my $dbh = shift;
    my $tablename = shift;

    my $fields = get_fields($dbh, $tablename);

    my $check_table = qq[
    SELECT 
        COUNT(*) AS cnt, 
        CONCAT(SUM(CONV(
            SUBSTRING(\@CRC:=MD5(
                CONCAT_WS('/##/',$fields)),1,8),16,10 )), 
        SUM(CONV(SUBSTRING(\@CRC, 9,8),16,10)),
        SUM(CONV(SUBSTRING(\@CRC,17,8),16,10)),
        SUM(CONV(SUBSTRING(\@CRC,25,8),16,10))
        ) AS sig 
    FROM 
        $tablename 
    ];

    # uncomment the following line to see the full query
    # print $check_table,$/;

    my ($count, $crc);
    eval { ($count, $crc) = $dbh->selectrow_array($check_table)};
    if ($@) 
    {
         return undef;
    }
    return [$count, $crc];
}

##</code><code>##

sub get_fields 
{
    my ($dbh, $tablename) = @_;
    
    my $sth = $dbh->prepare(qq[describe $tablename]);
    
    $sth->execute();
    
    my @fields=();
    while (my $row = $sth->fetchrow_hashref()) 
    {
        my $field ="`$row->{Field}`"; # backticks
        
        # if the field is nullable,
        # then a COALESCE function is used
        # to prevent the whole CONCAT from becoming NULL
        if (lc $row->{Null} eq 'yes') 
        {
            $field = qq[COALESCE($field,"#NULL#")];
        }
        push @fields, $field;
    }
    return join ",", @fields; 
}


##</code><code>##

#!/usr/bin/perl -w
use strict;
use DBI;

# for this test, we create the database handlers directly
# in the script
my $dbh1 = DBI->connect('dbi:mysql:test;host=localhost', 
        'localuser', 'localpassword', {RaiseError => 1});

my $dbh2 = DBI->connect('dbi:mysql:test;host=192.168.2.33;port=13330', 
        'remoteuser', 'remotepassword', {RaiseError => 1});

# this is the table to be created in both hosts
my $tablename = 'testcrc';

my $create = 
    qq{create table if not exists $tablename 
        (i int not null, j int, a char(1), b float )};

my ($table_exists) = $dbh1->selectrow_array(
        qq{SHOW TABLES LIKE '$tablename'});
        
if ($table_exists)
{
    # table exists. Let's make a tiny change
    $dbh1->do(qq{update $tablename set j = j-1 where i = 50});
}
else # table does not exists. Create and populate
{
    # create both tables
    $dbh1->do($create); 
    $dbh2->do($create);
    
    my $insert = qq{insert into $tablename values (?, ?, ?, ?)};

    my $sth1 = $dbh1->prepare($insert);
    my $sth2 = $dbh2->prepare($insert);

    # populates both tables with the same values
    for ( 1 .. 100 ) 
    {
        $sth1->execute($_, $_ * 100, chr(ord('A') + $_), 1 / 3 );
        $sth2->execute($_, $_ * 100, chr(ord('A') + $_), 1 / 3 );
    }
}
    
my %probes;

# gets the local table record count and CRC
$probes{'local'}  = get_table_CRC($dbh1, $tablename)
    or die "wrong info: $DBI::errstr\n";

# gets the remote table record count and CRC
$probes{'remote'} = get_table_CRC($dbh2, $tablename)
    or die "wrong info: $DBI::errstr\n";

# Checks the result and displays
print "LOCAL : @{$probes{'local'}}\nREMOTE: @{$probes{'remote'}}\n";

if (
    ($probes{'local'}->[0] != $probes{'remote'}->[0])
    or 
    ($probes{'local'}->[1] ne $probes{'remote'}->[1])
   )
{
    print "there are differences\n";
}
else 
{
    print "NO DIFFERENCES\n";
}