If you submit an update statement to a RDBMS in which the order of the column_name = value mappings don't match the physical layout of the file, does it affect (theoretically) the efficiency of the update operation?
I ask mainly out of curiosity, knowing full well that there's probably little effect.
If your DB engine is so poor as to be unable to optimize updates in this case, you certainly have worse problems to worry about:-(. IOW, there had better be no effect -- this is a matter of quality of implementation for the DB engine, but it's such a trivial one that I'd be appalled and astonished if it were otherwise.
No.
However, there are things you can do to improve UPDATE effciency, including only updating rows and columns that need to be updated.
I can say, in SQL Server and in Oracle, this is 'planned out' in the 'execution plan' stage and you will not notice a performance change when changing parameter ordering. I can't speak to some of the other 'less-enterprise' databases out there (SqLite, Firebird, Pervasive), but I expect that all databases will perform these steps when they parse the SQL statements into database operations.