The NULL statement takes no arguments.
The NULL statement performs no operation. It is used to indicate in an optional clause that no operation is to be performed when that clause is executed. It can be used within a THEN clause, an ELSE clause, or an ON ERROR clause. It is most commonly used in a THEN clause. For example:
WRITE mydata TO filevar,recID THEN NULL ELSE GOTO write_error PRINT "All done"
NULL transfers control to the statement immediately following the THEN...ELSE construction.