Screen Linkage Parameters - Answer

[Peter Bateman]

Darren:

The NULL flag is like another column when you add the constraint NOT NULL
its like dropping a column.

When PowerHouse first started supporting relational tables it did not
support NULL values. If you wanted QUICK to be able to access a column
in subscreen you had to reference the column in calling screen so that
the calling screen passed the table structure. Needless to say this was very 
annoying so
PowerHouse development changed that so that the whole table definition
as at compile time was sent. But that introduced the problem of the called 
and calling
list not macthing.

This can bite you when you least expect it.

Let suspose you add a column to the table. You don't recompile any screens.
Everything works as before.

Then later you compile one of the screen for other reasons.
  You suddenly now have the error message.

  Using CURSORs with fully qualified projection lists may help but not
  in the case of NULL/NOT NULL changes.

Regards,
Peter


>From: Darren Reely <darren.reely@latticesemi.com>
>CC: "'powerh-l@lists.sowder.com'" <powerh-l@lists.sowder.com>
>Subject: Re: Screen Linkage Parameters - Answer
>Date: Thu, 29 Apr 2004 11:33:43 -0700
>
>Hi again
>
>I have at least one confirmed possibility.
>
>I created a small table this morning and two screens. A calling screen (A) 
>and a called screen (B). I also left one of the column constraints as null 
>allowed during the initial table creation.. I compiled both screens and as 
>expected was able to call screen B from A.
>
>I then altered a column constraint to be NOT NULL.
>
>I again was able to successfully call screen B from A.
>
>Then I compiled one of the screens. It does not matter which one. When 
>calling screen B, from A I get the message described below.
>
>So it appears there is 'hidden' information compiled into the screen and 
>passed. I would have hoped since this is an Oracle table, that Powerhouse 
>would be able to work dynamically with this information, rather than 
>creating static information in the compiled code.  Oh well....
>
>Darren
>
>
>
>Darren Reely wrote:
>
>>Hi all,
>>
>>I'm getting the following error.
>>
>>       *d* The screen linkage parameters sizes are incompatible.
>>
>
>= = = = = = = = = = = = = = = = = = = = = = = = = = = =
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