Hi,
Looks like many people (even the official Joomla developers) looking for the same answer:
github.com/joomla/joomla-cms/issues/15629
issues.joomla.org/tracker/joomla-cms/15629
apparently many people suffering from the same problem. Thus proves that it is bug of Joomla Core. It happens because of the missing column (client_id) upon upgrading from certain Joomla versions (it happens to me as well on my localhost)
i found a solution that was suggested by
shajhan on
issues.joomla.org/tracker/joomla-cms/15629
He suggests and i quote;
you just go to admin > extension > database, click to button ‘Fix’ and recheck.
Yes, but BACKEND did´nt work anymore.
got some other Forum and tried this Solution.
COPY PATH BELOW AND PASTE ON YOUR WEBSITE
Just make a database Repair: YOURWEBSITE.COM/administrator/index.php?option=com_installer&task=database.fix
Now, Backend works and shows properly with Joomla 3.8.1
Try this and it should work. Simply navigate to this url:
YOURWEBSITE.COM/administrator/index.php?option=com_installer&task=database.fix
-- I tried on my localhost, and it fixed the problem for me. I don't get client_id error no more.
Regards.