On Monday 14 April 2008 17:44, Andreas Kretschmer wrote: > Garry Saddington <garry@xxxxxxxxxxxxxxxxxxxx> 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
