Per input file:

Once per command:
        /BY var_list[({D|A})] [var_list[({D|A})]]…

UPDATE updates a master file by applying modifications from one or more transaction files.

UPDATE shares the bulk of its syntax with other PSPP commands for combining multiple data files. See Common Syntax, above, for an explanation of this common syntax.

At least two FILE subcommands must be specified. The first FILE subcommand names the master file, and the rest name transaction files. Every input file must either be sorted on the variables named on the BY subcommand, or the SORT subcommand must be used just after the FILE subcommand for that input file.

UPDATE uses the variables specified on the BY subcommand, which is required, to attempt to match each case in a transaction file with a case in the master file: