/**
		 * Filters the part of the SQL query that performs the search.
		 *
		 * @since Unknown
		 *
		 * @param string             $sql           The SQL part that performs the search.
		 * @param LLMS_Student_Query $student_query Instance of LLMS_Student_Query.
		 */
		return apply_filters( 'llms_student_query_search', $sql, $this );
	}

	/**
	 * Set up the SQL for the select statement.
	 *
	 * @since 3.13.0
	 * @since 4.10.2 Drop usage of `this->get_filter( 'select' )` in favor of `'llms_student_query_select'`.
	 *               Use `$this->sql_select_columns({columns})` to determine additional columns to select.
	 * @since 5.10.0 Add a subquery for completed date.
	 *
	 * @return string
	 */
	private function sql_select() {

		$selects = array();

		// Always select the ID.
		$selects[] = 'u.ID as id';

		// Always add the subqueries for enrollment status.
		$selects[] = "( {$this->sql_subquery( 'meta_value' )} ) AS status";

		// All the possible fields.
		$fields = array(
			'completed'        => "( {$this->sql_subquery( 'updated_date', '_is_complete' )} ) AS completed",
			'date'             => "( {$this->sql_subquery( 'updated_date' )} ) AS `date`",
			'last_name'        => 'm_last.meta_value AS last_name',
			'first_name'       => 'm_first.meta_value AS first_name',
			'email'            => 'u.user_email AS email',
			'registered'       => 'u.user_registered AS registered',
			'overall_progress' => 'CAST( m_o_p.meta_value AS decimal( 5, 2 ) ) AS overall_progress',
			'overall_grade'    => 'CAST( m_o_g.meta_value AS decimal( 5, 2 ) ) AS overall_grade',
		);

		// Add the fields to the array of fields to select.
		foreach ( $fields as $key => $statement ) {
			if ( $this->requires_field( $key ) ) {