Is this bad design ?

Mother table.
fields:
mother_id
still_valid boolean
etc_fields

Child table
fields:
mother_id
still_valid boolean
more_fields

The child.still_valid field always contains a true, because only mothers withs are still_valid can have children, to enforce this; a relation is defined on the fields mother_id and still_valid.
(A child can not exist without its mother).

Because a field in the child table always has the same value, I think there is something wrong. But if this field is taken away a mother might become un_valid by another action.

Is this bad design ?
what is a alternative ?

(As I understand constraints should be implemented in the RDBMS and
not in the code).

ben brugman Received on Mon Mar 08 2004 - 10:11:32 CST