return $sql;
		}

		/**
		 * Filters the query JOIN clause
		 *
		 * @since 3.13.0
		 *
		 * @param string             $sql           The JOIN clause of the query.
		 * @param LLMS_Student_Query $student_query Instance of LLMS_Student_Query.
		 */
		return apply_filters( 'llms_student_query_join', $sql, $this );
	}

	/**
	 * Retrieve the prepared SEARCH query for the WHERE clause
	 *
	 * @since 3.4.0
	 * @since 3.8.0 Unknown.
	 * @since 4.10.2 Drop usage of `this->get_filter( 'search' )` in favor of `'llms_student_query_search'`.
	 *
	 * @return string
	 */
	private function sql_search() {

		$sql = '';

		if ( $this->get( 'search' ) ) {

			global $wpdb;