Re: Drop 'NOT NULL' Constraint

The command that worked was

ALTER TABLE table MODIFY column NULL;

This removed the NULL constraint but did not affect the data in the column.

Chris

"Deshpande, Kirti" wrote:
>
> Kevin,
> I don't think so. Here is what happens with a 8.1.7 database.
> SQL> create table t (ca varchar2(2) not null, cb number);
> Table created.
> SQL> insert into t values ('AA', 1);
> 1 row created.
> SQL> commit;
> Commit complete.
> SQL> desc t
> Name Null? Type
> ----------------------------------------- --------
> ----------------------------
> CA NOT NULL VARCHAR2(2)
> CB NUMBER
> SQL> select * from t;
> CA CB
> -- ---------------
> AA 1
> SQL> alter table t modify (ca null);
> Table altered.
> SQL> desc t
> Name Null? Type
> ----------------------------------------- --------
> ----------------------------
> CA VARCHAR2(2)
> CB NUMBER
> SQL> select * from t;
> CA CB
> -- ---------------
> AA 1
> SQL>
>
> If the column 'CA' were to have a primary key constraint, then the
> constraint needs to be dropped to modify the column as a nullable column.
>
> Regards,
>
> - Kirti Deshpande
> Verizon Information Services
> http://www.superpages.com
>
> > -----Original Message-----
> > From: Kevin Kostyszyn [SMTP:kevin_at_dulcian.com]
> > Sent: Wednesday, May 23, 2001 4:57 PM
> > To: Multiple recipients of list ORACLE-L
> > Subject: RE: Drop 'NOT NULL' Constraint
> >
> > I think that if there is already data in the column you will not be able
> > to
> > do that.
> >
> > -----Original Message-----
> > Sent: Wednesday, May 23, 2001 5:15 PM
> > To: Multiple recipients of list ORACLE-L
> >
> >
> > I created a table with a 'NOT NULL' constraint on a VARCHAR2 column. I
> > would like to remove the NOT NULL constraint. I've tried a couple of
> > 'ALTER TABLE' commands but no luck.
> >
> > How does one do this?
> >
> > Also:
> >
> > How does one figure out which generated constraints (from
> > user_constraints) do what?
> >
> > Chris Rezek
> > Database Administrator
> > DotClick
> > http://www.dotclick.com
> > --
> > Please see the official ORACLE-L FAQ: http://www.orafaq.com
> > --
> > Author: Chris Rezek
> > INET: crezek_at_dotclick.com
> >
> >
> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.com
> --
> Author: Deshpande, Kirti
> INET: kirti.deshpande_at_verizon.com
>
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-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.com
-- 
Author: Chris Rezek
  INET: crezek_at_dotclick.com

Fat City Network Services    -- (858) 538-5051  FAX: (858) 538-5051
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