sql独特的复合外键

Question

I have 2 tables:

group_config (id_group_config, owner_id, name_group_config)

group (id_group, id_group_config, name_group) - id_group_config is FK to group_config

So basically, a user (owner_id) creates a group_config, then creates a group which references this group_config. Pretty standard, but I want a constraint that the name_group must be unique per owner_id.

Only way I found to do this would be to replicate the owner_id on the group table too, which could cause inconsistencies.

Am I missing something?

thanks

Answer 1

Since a group_config can't exist without owner_id You should make the PK of group_config a composite PK consisting of owner_id and group_config_id. You need to be careful about referential integrity constraints here eg what happens when you delete an owner?

This will automatically make the FK in group be that composite key.

To make the name_group unique per owner in group table, you create a unique index composed of the columns owner_id and the name_group.