original post now deleted after addition of Edit #2. Was totally incorrect.
Based upon your comment have deleted above.
Have tested the sample in the link provided and have had problems. While I can add new records (as shown), and I can modify the name field, changing an existing department using this method (query) produces the error shown - this on Ubuntu 18.04 using LO v220.127.116.11.
As asked in comment please elaborate on what you are looking to accomplish and there may be a different method.
OK, have found the problem with the linked post answer. It is in the Query. Using the
Right Outer Join is the cause. But to correct the situation had to use a different method only through
SQL View. Therefore you cannot use the graphical interface. Have attached a sample based upon you original post. This sample does NOT include the macro referred to in the linked post. You can add that if you wish a refreshed list after each modification. Up to You.
sample ---- FKproblem.odb