protected function get_sql_clause_for_member_types( $member_types, $operator ) {
		global $wpdb;

		// Sanitize.
		if ( 'NOT IN' !== $operator ) {
			$operator = 'IN';
		}

		// Parse and sanitize types.
		if ( ! is_array( $member_types ) ) {
			$member_types = preg_split( '/[,\s+]/', $member_types );
		}

		$types = array();
		foreach ( $member_types as $mt ) {
			if ( bp_get_member_type_object( $mt ) ) {
				$types[] = $mt;
			}
		}

		$tax_query = new WP_Tax_Query( array(
			array(
				'taxonomy' => bp_get_member_type_tax_name(),
				'field'    => 'name',
				'operator' => $operator,
				'terms'    => $types,
			),
		) );

		// Switch to the root blog, where member type taxonomies live.
		$site_id  = bp_get_taxonomy_term_site_id( bp_get_member_type_tax_name() );
		$switched = false;
		if ( $site_id !== get_current_blog_id() ) {
			switch_to_blog( $site_id );
			$switched = true;
		}

		$sql_clauses = $tax_query->get_sql( 'u', $this->uid_name );

		$clause = '';

		// The no_results clauses are the same between IN and NOT IN.
		if ( false !== strpos( $sql_clauses['where'], '0 = 1' ) ) {
			$clause = $this->no_results['where'];

		// The tax_query clause generated for NOT IN can be used almost as-is. We just trim the leading 'AND'.
		} elseif ( 'NOT IN' === $operator ) {
			$clause = preg_replace( '/^\s*AND\s*/', '', $sql_clauses['where'] );

		// IN clauses must be converted to a subquery.
		} elseif ( preg_match( '/' . $wpdb->term_relationships . '\.term_taxonomy_id IN \([0-9, ]+\)/', $sql_clauses['where'], $matches ) ) {
			$clause = "u.{$this->uid_name} IN ( SELECT object_id FROM $wpdb->term_relationships WHERE {$matches[0]} )";
		}

		if ( $switched ) {
			restore_current_blog();
		}

		return $clause;
	}