# check tableName
    #TODO check that the table exists in the database
    # or die "Error: table does not exist: $tableName\n";

    #  set up database
    my $db = $cuiFinder->_getDB(); 
    
    # retreive the table as a nested hash where keys are CUI1, 
    # then CUI2, value is N11
     my @keyFields = ('cui_1', 'cui_2');
     my $matrixRef = $db->selectall_hashref(
        "select * from $tableName", \@keyFields);

    # set values of the loaded table to n_11
    # ...default is hash of hash of hash
    foreach my $key1(keys %{$matrixRef}) {
        foreach my $key2(keys %{${$matrixRef}{$key1}}) {
            ${${$matrixRef}{$key1}}{$key2} = ${${${$matrixRef}{$key1}}{$key2}}{'n_11'};
        }
    }
    return $matrixRef;
}