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Tip of the Day
Language: SQL
Expertise: Beginner
May 29, 1997

What type of code to write if NOT NULL messages must be avoided

Question:
What type of code must be written to avoid the cryptic NOT NULL messages when records are to be added for fields already defined with NOT NULL in the table definitions?

Answer:
The NOT NULL message is not that cryptic. It indicates that a required field, one that is not allowed to be null, does not have a value when the row containing the field is written to the database.

It's fairly easy to check for this. At the appropriate place, you would use the ISNULL() method for the Value property of the fields linked to the table's NOT NULL columns.

But where is the appropriate place? You have to do it before the row gets to the database. OPO will flush a row to the database in a variety of circumstances, such as moving to another container. The whole point of this corrective action is to inform users of a problem while they can still fix it; for me, this means before they navigate to another row. I would use the Go... methods for this logic. It probably makes sense to add this logic to a user-defined method and call it from both Go... methods.

In my new book, Mastering Oracle Power Objects from O'Reilly & Associates, I explain how to create a class that will make this even easier to implement.

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