Re: simple questions-cannot find answers in common books

Paul King wrote:

> I too have only used matching indicators one, many years ago, but my
> recollection of these is that the program would continue reading from each
> file until the key in BOTH changed, thus, detail records which had no header
> records in the related file, for example, would still be returned to the
> program, as would header records with no detail, the presece of either, or
> both, being indicated by the assigned file indicator being on or off..

Actually, the clearest way of thinking about matching record indicators and
their function is that they provide a way to key-merge records from different
files and possibly different formats into a single steam of records.  The MR
indicator comes on when you are processing files from either the primary or any
of the secondary files that match the key values in the other files at that
moment.

> This provides functionality which (to the best of my knowledge) still isn't
> available in SQL, i.e. an outer join (if thats the right way of phrasing it
> - I'm not an SQL guru), rather than the normal two statements, one left join
> and one right join, then some horrible code to stick the extracted data
> together.

Yup, NOT an outer join.  As I pointed out earlier, a merge.  The only other
convenient way that I know of doing this is to build a mult-format logical over
multiple physical files.

> The downside I seem to recall is that it only works with the RPG
> cycle. Is my recollection correct - or not?!
>

Yup, MR only comes on with the use of primary and secondary files in the RPG
cycle.  The M1 thru M9 indicators are used like L1 thru L9 indicators, but
instead match the "key" fields between primary and secondary files.  The RPG
cycle must do the reads and the records are returned to the program one by one.

--
===========================================================
R. Bruce Hoffman, Jr. -- IBM Certified AS/400 Administrator

-- The sum of all human knowledge is a fixed constant.
    It's the population that keeps growing!


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