完整的bug信息：

ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'mysqldump -uroot -p ylt>ylt.sql' at line 1

错误原因是我误以为mysqldum是sql命令，错误写入了mysql命令中

mysql> mysqldump -uroot -p ylt>ylt.sql;

后才发觉mysqldump是linux命令

遂退出mysql，在终端写入

[root@localhost ~]# mysqldump -uroot -p ylt>ylt.sql

这样就对了