mysql服务启动失败

[root@training ~]# systemctl start mysql
Job for mysqld.service failed because the control process exited with error code. See "systemctl status mysqld.service" and "journalctl -xe" for details.

[root@training ~]# systemctl status mysql
● mysqld.service - LSB: start and stop MySQL
   Loaded: loaded (/etc/rc.d/init.d/mysqld; bad; vendor preset: disabled)
   Active: failed (Result: exit-code) since Sun 2018-05-06 10:06:53 CST; 26min ago
     Docs: man:systemd-sysv-generator(8)
  Process: 29770 ExecStart=/etc/rc.d/init.d/mysqld start (code=exited, status=1/FAILURE)

May 06 10:06:52 training systemd[1]: Starting LSB: start and stop MySQL...
May 06 10:06:53 training mysqld[29770]: Starting MySQL.The server quit without updating PID file (/usr/local/mysql/data/mysql/training.pid).[FAILED]
May 06 10:06:53 training systemd[1]: mysqld.service: control process exited, code=exited status=1
May 06 10:06:53 training systemd[1]: Failed to start LSB: start and stop MySQL.
May 06 10:06:53 training systemd[1]: Unit mysqld.service entered failed state.
May 06 10:06:53 training systemd[1]: mysqld.service failed.