If you are trying to update your Joomla site using the Joomla! Update component in your backend to the latest Joomla version, you may receive an error during the update process or after the update attempts to complete. The failed Joomla update renders your Joomla website completely useless and you are stuck with a non-functioning website suddenly!
Error displaying the error page: Unknown column 'a.client_id' in 'where clause': Call to undefined method JApplicationAdministrator::isClient()
And or…
Call to undefined method JApplicationSite::isClient()
There is a known bug upgrading certain versions of Joomla 3.x to 3.6, 3.7 or 3.8 which cause these messaged. Luckily, there is a post-manual script developed which will recover your Joomla site and complete the update process succesfully. Follow the steps below.
Error displaying the error page: Unknown column 'a.client_id' in 'where clause': Call to undefined method JApplicationAdministrator::isClient()
\Joomla Root Folder\administrator
myjoomlasite.com\administrator\postupdate.php
To learn more about the post-manual update scrip for Joomla, visit GitHub here.
Comments
This worked like charm. God bless the author of this help.