Constraints on NULLable columns

  Oracle7 Server Release 7.3.4.0.1 - Production and also on
  Oracle8 Enterprise Edition Release 8.0.5.1.0 - Production

SQL> create table tmp (x integer);
Table created.

SQL> alter table tmp add constraint foo check (x > 0); Table altered.

SQL> insert into tmp values (null);
1 row created.

SQL> select count(*) from tmp where x > 0;   COUNT(*)

         0

SQL> select count(*) from tmp;
  COUNT(*)

         1

  Why doesn't adding the "foo" constraint to the x column stop nulls from being added? I know I could just make the column NOT NULL but shouldn't adding that constraint have the same effect?

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Reality is a cheap substitute for Prozac Received on Thu Oct 21 1999 - 17:58:11 CDT