OK i got it to update one row at a time like
update tblFPPets
set AcctNum = LicenseNum, LicenseNum = null
where DateLicenseExpires < getdate() and OwnerID_FK = 8
but when i try to do it on the entire database like
update tblFPPets
set AcctNum = LicenseNum, LicenseNum = null
where DateLicenseExpires < getdate()
i get this error
Server: Msg 2627, Level 14, State 2, Line 1
Violation of UNIQUE KEY constraint 'UQ__tblFPPets__0880433F'. Cannot insert duplicate key in object 'tblFPPets'.
The statement has been terminated.