Re: Show nulls on display file?

A good use of null is employee retirement data (or leaving for any reason) Usually you do not know when they will leave, so set it to null. Some will suggest *hival 9999-12-31, and it will work most of the time, but all current employees will come out if you SELECT * FROM E WHERE LEAVING >= '2017-01-01' not only the ones that leaved this year.

What should be the water temperature when the tank is empty?


On 02/22/2017 03:00 PM, Charles Wilt wrote:

I disagree...

NULL can be very useful. But, it's often overused and/or misused.

Consider NULL when it has different meaning than a type default (0,
blank/empty, 9999-12-31/0001-01-01)

For example, a column for "Address line 2" is often "optional"; a user may
or may not enter it. But does my application really need to differentiate
between "not entered" and "entered blanks"? Probably not.

Consider "Expiration date", "never expires" is a valid choice. NULL might
used for that. But from a business standpoint, it's probably easier to
simply "never expires" isn't allowed. Instead, we'll allow an expiration
date of 9999-12-31; that's close enough to "never" for most people. Now
perhaps we can use NULL to mean "unknown" - and we need to find out what
that actual expiration should be.

In the Op's case, he needs to differentiate between entered 0 and not
entered. Allow NULL is a reasonable solution. His alternatives
1) Flag field (is just an application defined null-bit)
2) Magic Number, -1 perhaps. Since I suspect the "valid" values for this
field are >= 0. But now instead of checking for NULL, you're checking for
-1.
3) Storing the column as a NOT NULL in it's own table.

Option 3 is usually branded about as a way around allowing NULL in the DB.
But from an application/UI standpoint you still have to deal with NULL
since a record may or may not exist.

NULL isn't really the problem here, it's the limits of the 5250 UI.

The BLANKS keyword I suggested is a possible solution...

Charles



On Wed, Feb 22, 2017 at 8:35 AM, Henrik Rützou <hr@xxxxxxxxxxxx> wrote:

DB null capable fields is something the devil has created to make life
miserable for programmers!

On Wed, Feb 22, 2017 at 4:07 PM, Raul A Jager W <raul@xxxxxxxxxx> wrote:

You need to show only or also read?

Will blank mean null and zero the value zero? To display you can use
%editc() to move to a char field if not null, and clear the field if

null.

You need to validate only if you need to read the field.


On 02/21/2017 06:17 PM, Bob Cagle wrote:

Is there a way to display a null value on a display file? I have a user
requesting that a 2-digit numeric field show either blanks or zero as

well

as 1 - 99, emulating Excel-like behavior.

The only solution I can think of is to convert it to a character field
and validate for numeric or blank. Suggestions?

Thanks

Bob Cagle
IT Manager
Lynk

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