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Nov 11, 2015
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Feb 19, 2013
Nulls in Date Fields NEW
by: Grant

In my experience, we would use a default date (like low date) in a date field to indicate it is unknown. So if the delivery has not occurred yet, put low-date in there as the default. Now you can sort on it, and easily count the number of undelivered orders.

I have worked with a database system where every field is defined as NOT NULL WITH DEFAULT. This makes programming, querying, sorting, and so forth much easier. In other words, every field in the database has a value, per standard database design and practice.

Feb 16, 2011
null value
by: Anonymous

i think it is again the case of denormilization. DeliveredOn column need not be on the order table.
It can be in a different table named "delivery" (or something like that )and contains the columns "order id" and "DeliveredOn", both cannot hold null.

Now if there is an entry in the delivery table for an order, then it is delivered else it is not.

Sep 30, 2010
Right, but wrong.
by: Alf


Yes, I can see where you're at, but read again the first paragraphs of my article, and especially Codd's definition.

The purpose of a database is to be delivering true propositions (Yes) or negatives (No). A "Maybe" does not do either. It just states that we don't know if it has been delivered. It could have been, but has not yet been entered into the system, etc.

It is not our fault that we sometimes must create a row like yours: It is the way DBs are implemented (A complete row, rather than individual columns.

But I hope you will read this:

Forum post on new perspectives

and check up on Sand model too. It is very interesting: It will make DBs MUCH faster as well as the need for NULLs are non-existent.

But today, if you use Oracle, SQLServer, MySQL etc., I would probably use your construct :-) . But it doesn't make it any more correct: It is against the definition of relational.

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