O$: Null Fields

[Joe Maus]

----- Christine Penner <christine at ingenioussoftware.com> wrote:
> I have looked through the past discussions on nulls. I asked a 
> similar question before but they are all more general then what I'm 
> looking for. We have decided that we will be dealing with nulls. What 
> I want is some suggestions on how to deal with specific things like 
> the example I gave. I could write a pile of code checking nulls but I 
> thought someone may have a more elegant solution then what I would 
> come up with.
...

If (pOldRow.FF_HIRED<>pNewRow.FF_HIRED)|(pOldRow.FF_PREVIOUS_MONTHS<>pNewRow.FF_PREVIOUS_MONTHS)...

Your options are limited.  One choice is to select an empty back when the column is null.  This has the advantage of populating your list columns for you on the select and if you have but one select for that particular need, then all code that uses that select will have the columns populated.  That is, you call something like oSQL.sel_my_table and within that method you do something like "select isnull(col1,'')..." and you ALWAYS call oSQL.sel_my_table whenever you need data from that table wherever needed in your application then this will work.  If you're doing listname.$select() then obviously this won't work.  (I suggest you adopt a single object to hold all of your sql code (if you have not already done so) if only because it assures you have the same sql for all calls made for that data in your application.  Much easier to maintain if there is only ever one place to get a specific set of data...)

The other is to do the "pick" trick:

If (pOldRow.FF_HIRED<>pNewRow.FF_HIRED)|(pick(isnull(pOldRow.FF_PREVIOUS_MONTHS),(pOldRow.FF_PREVIOUS_MONTHS<>pNewRow.FF_PREVIOUS_MONTHS),kfalse)

presuming the FF_HIRED column is never null.  There is also a new function, "isclear" I believe, in newer versions of Studio that is supposed to do the same thing as the pick, in effect anyway.

Note the user's tabbing though the column on the window will change a null to an empty which can cause some "interesting" behavior depending on what your desired outcome is.

Regards,

Joe Maus