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 The Use of Nulls

Author  Topic 

MichaelP
Jedi Yak

2489 Posts

Posted - 2003-06-17 : 17:54:30
This is a design question.

Let say I have an INT field in a table called PagesToPrint. Sometimes, users will want a finite number of pages, other times they want "all". There's no way for me to calculate how many pages "all" is, so I was thinking of using NULL to indicate "all"

That would give me values like:
0
5
100
NULL


Does using Null in this way make sense? Is it a valid technique? Is there a better way? I do this sort of thing quite often, and I always feel like it's a "hack" or something.

Any advice would be greatly appreciated!

Michael

<Yoda>Use the Search page you must. Find the answer you will.</Yoda>

robvolk
Most Valuable Yak

15732 Posts

Posted - 2003-06-17 : 19:00:24
It's not a hack IMHO, but you can still use some other replacement value if you want. Something like 1,000,000 would work too, if anyone actually needs to print more than 1 million pages they messed up anyway. That way you don't have to add any particular logic to work around the null.

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byrmol
Shed Building SQL Farmer

1591 Posts

Posted - 2003-06-17 : 19:14:55
Michael,

Because I really dislike NULLs, I would go with a value as Rob suggested. I would have thought -1 would be a good candidate...
And another thing why a INT? Surely a SMALLINT would do nicely..

Whatever you choose.. document it!

DavidM

"SQL-3 is an abomination.."
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robvolk
Most Valuable Yak

15732 Posts

Posted - 2003-06-17 : 19:18:58
quote:
I would have thought -1 would be a good candidate...
Yeah, I thought of that too

I guess if two people come up with the same idea independently, then it's probably a good idea....

....or they're psychic somehow.

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MichaelP
Jedi Yak

2489 Posts

Posted - 2003-06-17 : 19:46:08
You never know when you have that 2 billion page report!!!

Actually, this was just an example of what I'm trying to do. I think I like -1 and a SmallInt field.

Thanks all!!

Michael



<Yoda>Use the Search page you must. Find the answer you will.</Yoda>
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byrmol
Shed Building SQL Farmer

1591 Posts

Posted - 2003-06-17 : 19:50:55
Rob,

I used -1 so that it would be in the range of the smallint! And quite frankly I see users "mess up" all the time and I can imagine the toner bill after a few of those stuff up ;-)

DavidM

"SQL-3 is an abomination.."
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