Source

File: wp-admin/includes/class-wp-site-health.php

private function prepare_sql_data() {
		global $wpdb;

		if ( $wpdb->use_mysqli ) {
			// phpcs:ignore WordPress.DB.RestrictedFunctions.mysql_mysqli_get_server_info
			$mysql_server_type = mysqli_get_server_info( $wpdb->dbh );
		} else {
			// phpcs:ignore WordPress.DB.RestrictedFunctions.mysql_mysql_get_server_info,PHPCompatibility.Extensions.RemovedExtensions.mysql_DeprecatedRemoved
			$mysql_server_type = mysql_get_server_info( $wpdb->dbh );
		}

		$this->mysql_server_version = $wpdb->get_var( 'SELECT VERSION()' );

		$this->health_check_mysql_rec_version = '5.6';

		if ( stristr( $mysql_server_type, 'mariadb' ) ) {
			$this->is_mariadb                     = true;
			$this->health_check_mysql_rec_version = '10.0';
		}

		$this->mysql_min_version_check = version_compare( '5.5', $this->mysql_server_version, '<=' );
		$this->mysql_rec_version_check = version_compare( $this->health_check_mysql_rec_version, $this->mysql_server_version, '<=' );
	}