[SOLVED] Error 500 during login after upgrade to 9.0.1

[dokmaiste38]

I  have upgraded Prestashop from 8.1.1 to 9.0.1. Everything worked fine but I am unable to login into the admin backend.

Below is the log when I submit the login form:

request.CRITICAL: Uncaught PHP Exception Doctrine\ORM\NonUniqueResultException: "More than one result was found for query although one row or none was expected." at AbstractQuery.php line 973 

The error was as follows:

 

The solution was to delete old, additional records for my user from the table ps_employee.

I hope this helps someone else!

Edited November 21 by dokmaiste38
typo (see edit history)