protected function get_comparison() {

		if ( ! $this->column ) {
			return '';
		}

		$query = "{$this->column} ";

		if ( is_array( $this->value ) ) {
			$values = $this->implode( $this->value );

			if ( $this->operator ) {
				$query .= "IN ($values)";
			} else {
				$query .= "NOT IN ($values)";
			}
		} elseif ( $this->value === null ) {

			if ( $this->operator === true || $this->operator === '=' ) {
				$query .= 'IS NULL';
			} else {
				$query .= 'IS NOT NULL';
			}

		} else {

			if ( is_bool( $this->operator ) ) {
				$operator = $this->operator ? '=' : '!=';
			} else {
				$operator = $this->operator;
			}

			$query .= "$operator '{$this->value}'";
		}

		return $query;
	}