[Gnumed-devel] Uniqueness in dem.lnk_identity2ext_id

[Jim Busser]

Schema gnumed_v14

        table dem.lnk_identity2ext_id

includes:

***************************************************************************
dem.identity.pk                 id_identity     UNIQUE#1 NOT NULL

                                                external_id     UNIQUE#1 NOT 
NULL 

dem.enum_ext_id_types.pk        fk_origin       UNIQUE#1 NOT NULL 
***************************************************************************

so I just wondered... yes, any one person can have multiple external IDs 
therefore I understand that dem.identity.pk cannot be required to be unique by 
itself. I only just wondered about dem.identity.pk being part of the constraint 
of

        {external_id, fk_origin}

being unique, since it allows different persons to have the same

        {external_id, fk_origin}

but I then realized that in some cases a single external organization 
(fk_origin) might re-use the same external_id for multiple persons (maybe an 
account number used in common by a family). In other cases, the issuer would 
NOT intend re-use across two different persons.

Would it work in dem.enum_ext_id_types to add the column

        isunique

allowing to constrain the second scenario? That way, UNIQUE#1 NOT NULL could be 
removed from from id_identity and it could be the

        isunique = FALSE

that would determine if replicates of

        {external_id, fk_origin}

could be allowed in a table?

-- Jim