This indicates MySQL database corruption. Your best bet at this point is to run a mysql check. This can be done from a command-line that you would log in to as admin.
Once you are logged in, run this command:
cc-config database --check --repair
Run this 2 times to make sure it is able to correct as many tables as possible. If this does not fix the issue, the best option for you is to restore the appliance back to a default install of 9.0.1 and restore from your most recent backup.