我有一个Apache服务器，重新启动服务器后无法启动MYSQL。当我应用“ service mysql start”或“ service mysql restart”时，我在SSH上收到此错误：
MySQL server PID file could not be found! [FAILED]
Starting MySQL.The server quit without updating PID file (/var/lib/mysql/server.xxx.org.pid). [FAILED]
我检查了错误日志，错误如下：
2018-08-20 15:43:44 8511 [ERROR] /usr/sbin/mysqld: Table './mysql/db' is marked as crashed and should be repaired
2018-08-20 15:43:44 8511 [ERROR] Fatal error: Can't open and lock privilege tables: Table './mysql/db' is marked as crashed and should be repaired
如何解决此问题？