2013/2/5 Darren Duncan <darren@xxxxxxxxxxxxxxxx>: > I'd like to know what value there is in making NOT NULL and CHECK > deferrable. Consider such schema sample: - you have tables “groups” and “group_items” - each group must have at least one item - each group must have a “master” item, that is denoted in groups.master_item_id column - groups.group_id, groups.master_item_id, group_items.item_id and group_items.group_id should be NOT NULL - you use “serial” type for the KEY columns Now, when you're creating a new group: - you cannot insert a row into the groups, as master_item_id is not yet known and NULL is not allowed; - you cannot insert a row into the group_items, as you need to know group_id, FK can be deferred, but NULL is not allowed. All this works pretty good if one don't use “serial” type for the keys and explicitly calls nextval() on the corresponding sequences first. -- Victor Y. Yegorov -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
