将 PHP 从 5.6 版升级到 7.2 版后，MySQL 服务无法在 Ubuntu 14.04 上启动

Question

我已将 PHP 从版本 5.6 升级到 7.2，现在 MySQL 无法工作。当我输入 时sudo service mysqsl start，会显示以下文本：

Job for mysql.service failed because the control process exited with error code.
See "systemctl status mysql.service" and "journalctl -xe" for details.

输出 journalctl -xe

输出systemctl status mysql.service：

mysql.service - LSB: Start and stop the mysql database server daemon
   Loaded: loaded (/etc/init.d/mysql)
   Active: failed (Result: exit-code) since \u0633\u0647\u200c\u0634\u0646\u0628\u0647 2018-07-17 04:22:01 +0430; 27s ago
     Docs: man:systemd-sysv-generator(8)
  Process: 26938 ExecStop=/etc/init.d/mysql stop (code=exited, status=0/SUCCESS)
  Process: 6860 ExecStart=/etc/init.d/mysql start (code=exited, status=1/FAILURE)
 Main PID: 9974 (code=exited, status=0/SUCCESS)

\u0698\u0648\u0626\u06cc\u0647 17 04:22:01 hutadmin-virtual-machine mysql[6860]: [97B blob data]
\u0698\u0648\u0626\u06cc\u0647 17 04:22:01 hutadmin-virtual-machine mysql[6860]: Fatal error in defaults handling. Program aborted
\u0698\u0648\u0626\u06cc\u0647 17 04:22:01 hutadmin-virtual-machine /etc/init.d/mysql[7565]: 0 processes alive and '/usr/bin/mysqladmin --defaults-file=/etc/mysql/debian.cnf ping' resulted in
\u0698\u0648\u0626\u06cc\u0647 17 04:22:01 hutadmin-virtual-machine /etc/init.d/mysql[7565]: [61B blob data]
\u0698\u0648\u0626\u06cc\u0647 17 04:22:01 hutadmin-virtual-machine /etc/init.d/mysql[7565]: error: 'Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2)'
\u0698\u0648\u0626\u06cc\u0647 17 04:22:01 hutadmin-virtual-machine mysql[6860]: ...fail!
\u0698\u0648\u0626\u06cc\u0647 17 04:22:01 hutadmin-virtual-machine systemd[1]: mysql.service: Control process exited, code=exited status=1
\u0698\u0648\u0626\u06cc\u0647 17 04:22:01 hutadmin-virtual-machine systemd[1]: Failed to start LSB: Start and stop the mysql database server daemon.
\u0698\u0648\u0626\u06cc\u0647 17 04:22:01 hutadmin-virtual-machine systemd[1]: mysql.service: Unit entered failed state.
\u0698\u0648\u0626\u06cc\u0647 17 04:22:01 hutadmin-virtual-machine systemd[1]: mysql.service: Failed with result 'exit-code'.

我该如何解决这个问题？我需要启动 MySQL。