mysql5.7 help mysqldump 显示 nothing found 是不是不正常?该怎么解决

mysqldump -u root -p --all-databases > database_dump.txt;
连这种语句我敲进去都返回:
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 -u root -p --all-databases > database_dump.txt' at line 1
我就好气,我想不会是我 mysqldump 没有吧...
于是 help mysqldump 返回

mysql> help mysqldump;

Nothing found
Please try to run 'help contents' for a list of all accessible topics

请问各位的 help mysqldump 也是这样的么..
我的数据库没带 mysqldump???
咋解决啊
谢谢