> I currently have the scenario where I need to add a single CHAR(1) column
> to a 250m row table and populate it with a constant value (new records may
> have a different value). The approach I am considering is:
>
> 1) alter table blah add (mycol char(1));
> 2) update blah set mycol = 'F '; {perhaps include a parallel hint on
> this statement}
> 3) alter table blah modify mycol not null enable novalidate;
You should use:
alter table t add c char(1) default 'F ' not null;
alter table t modify c default null;
That way you would avoid the additional update and enable constraint
clauses.
> SQL > alter table blah modify mycol not null enable novalidate;
...
> This is happening on Oracle 8.1.7.4 (running on Solaris) and is
repeatable.
> Whenever "enable novalidate " is used the constraint doesn 't appear.
Trying
> to insert null data shows the constraint is actually there, just not
> appearing in describe.
It 's just the way DESC clause in sqlplus queries the cdef$ and ccol$ data
dictionary tables. It only shows validated not null constraints there,
probably for consistency with Oracle optimizer behaviour, which cannot take
a not validated constraint seriously when optimizing execution plans.
You can still see your constraint from dba_constraints, you just see it 's
not validated from there.
Tanel.
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