Your suggested syntax is good, IMO. In fact, it is very similar to the Tutorial D database language :
user RENAME ( login AS username )
will project all 14 attributes from relvar userwith one renamed as indicated.
Similarly, Tutorial D has a design statement ALL BUT, for example.
user { ALL BUT login }
will result in a ratio of 13 attributes in your case.
, SQL , , . , , , SELECT * ; ! , SQL, SELECT * BUT <commalist> SQL, . SELECT * !