UniBasic Commands Reference - Rocket Software

READBCK
Syntax
READBCK dyn.array.var [FROM file.var] [ON ERROR statements] {THEN
statements [END] | ELSE statements [END]}
Description
The first READBCK command retrieves the alternate key set by SETINDEX, then
each subsequent READBCK retrieves the previous alternate key value in the index.
The corresponding record is read into a dynamic array, and the record ID is assigned
to the @ID variable.
Note: This command does not check for locks. If you are operating in a multiuser
environment, you must use record locks to prevent more than one user from accessing
the same record at the same time. For more information about UniBasic record
locking, see Developing UniBasic Applications.
Using this command in a loop, a UniBasic program retrieves records in descending
order based on an indexed attribute.
Before executing READBCK, you must set the alternate key value with the
SETINDEX command. The SETINDEX parameters BUFFER.KEYS and
VALIDATE.KEY determine, respectively, whether the buffering mechanism is used
and whether keys are validated when READBCK executes. For details, see
SETINDEX.
READBCK sets the STATUS function return value to 10 if UniBasic detects a
duplicate alternate index key value and you have executed the ECL command
DUP.STATUS ON during the current session.
READBCK 1-599