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" Regards, Andreas -- Really, I'm not out to destroy Microsoft. That will just be a completely unintentional side effect. (Linus Torvalds) "If I was god, I would recompile penguin with --enable-fly." (unknow) Kaufbach, Saxony, Germany, Europe. N 51.05082°, E 13.56889°
