On Monday 14 April 2008 17:44, Andreas Kretschmer wrote:
> Garry Saddington <garry(at)schoolteachers(dot)co(dot)uk> schrieb:
> > How would I write a table check constraint to make sure that two columns
> > don't both have nulls at the same time.
> > The following doesn't do it because it because it does not allow one
> > column to be null while the other holds data?
> >
> > check(teachgroup is not null AND set is not null)
>
> test=# create table not_null (a int, b int, check((a is not null) or (b is
> not null))); CREATE TABLE
> test=*# insert into not_null values (1,1);
> INSERT 0 1
> test=*# insert into not_null values (1,NULL);
> INSERT 0 1
> test=*# insert into not_null values (null,2);
> INSERT 0 1
> test=*# insert into not_null values (null,null);
> ERROR: new row for relation "not_null" violates check constraint
> "not_null_check"
Works great, thanks
regards
garry