System error 5 occurred and access was denied when MySQL was restarted in CMD, as shown below:

This error is caused by insufficient permissions to operate CMD. The solution is as follows:
Enter CMD in the search bar of the start menu, right-click the search results, and select run as administrator!

If the frequency of CMD use is high, the following is a once-and-for-all method:
1. Right click on Cmd and select “Attend to Start Menu (U)” to find Cmd in Start Menu.
2. Right-click to select properties, select shortcut, then select advanced, select to run as administrator, and then click OK!
Just open the Start menu and click the shortcut above to run CMD as an administrator!
Net start mysql = net start mysql = net start mysql
 
 
In addition, some prompt that the server name is invalid

 
Different MySQL may have different names
Therefore, it needs to be modified to
Net start MySQL56