<dianeb77@...> wrote:

> The SQL standard says that when you add the new column, the value of
> that column in each row is set to the default value for the column.
>
> As someone quoted in another message, the SQL92 rules say:
> "1) The column defined by the <column definition> is added to T.
> 2) Let C be the column added to T. Every value in C is the default
> value for C."
>
> If there is no explicit default value specified (for the
> column or the
> domain), then the default value is the null value.
> If that would cause a constraint (such as NOT NULL) to be violated,
> then an exception should occur, and the alter statement
> should have no
> effect.
>
> In the SQL92 standard, the evaluation of constraints can be deferred,
> which would allow you to alter the table to add the column (violating
> the constraint, if it were checked at that point), then assign values
> to the columns as a separate step, then have the constraint checking
> done.

Thank you, Diane.

Cheers,
Dmitry