Re: Can't RPG Update a NULL Field?

Partly right - non-varying length fields ARE contiguous as far as I can remember. There are pointers of a sort to an auxiliary space for data longer than the allocated length of varying length fields.

We also need to be careful about NOT saying a field has a NULL value - NULL is NOT a value - it is a state, an attribute - that is why SQL has the test WHERE FIELD IS NULL - not WHERE FIELD = NULL

Are we having fun yet?

Vern

-------------- Original message ----------------------
From: "Michael Naughton" <michael_naughton@xxxxxxxxxxxx>

This is just a guess, but I know in other systems when a field has a value of
"null" it basically means the field doesn't exist. IIRC, the iSeries doesn't
store fields in records contiguously, necessarily; instead, it puts them
wherever and then uses
pointers to locate them. Might a field with a null value be a field with no
pointer (i.e. the iSeries hasn't yet allocated any storage space for it)? In
which case, how would you update it -- where would the value go? Initializing
the field to a default
value then means that it _has_ been created, and therefore it can be updated.

Just a guess . . .

Midrange Systems Technical Discussion <midrange-l@xxxxxxxxxxxx> writes:

Riddle me this...I was trying to update a record using the RPG UPDATE
opcode. I first tried the %Fields parm (which I usually use), and the
fields weren't being updated. So I took off the %Fields - no change. I
had specified H AlwNull(*UsrCtl), which I thought would allow me to do
as I pleased with a null field. It wasn't until is set the fields that
I was trying to update to their default values (zeros, blanks) that I
was able to programmatically update the fields that contained a null.
Is this WAD or am I missing something? Thanks...

Mike Naughton
Senior Programmer/Analyst
Judd Wire, Inc.
124 Turnpike Road
Turners Falls, MA 01376
413-863-4357 x444
mnaughton@xxxxxxxxxxxx
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