public function isDisplayNameExists( $displayName, $excludeId = null )
    {
        $platform = $this->getDbAdapter()
                         ->getPlatform();

        $expr = new Predicate\Expression(
            'LOWER( ' . $platform->quoteIdentifier( 'displayName' ) .
                ' ) = LOWER( ? )', $displayName
        );

        return $this->isExists( empty( $excludeId ) ? array(
            $expr,
        ) : array(
            $expr,
            new Predicate\Operator(
                'id',
                Predicate\Operator::OP_NE,
                $excludeId
            ),
        ) );
    }