On 08/13/2015 05:03 PM, Stephen Feyrer wrote:
Hi,This is probably not an original question merely one which I haven't been able to find an answer for. Basically, the question is why is there not an equivalent foreign key concept to match the primary key we all already know an love? How this would work, would be that the foreign key field in the host table would in fact simply be a reference to a key field in the guest table. Then in the respective SQL syntax a semantic reference may then be made whether or not to follow such links. Therefore as an example: {system:{"primary-key":"1","child-key":"","date":"20150421","directory-name":"Bucket List","user-attribute":"bucket.l...@example.com"}, {"primary-key":"2","child-key":"","date":"20150421","directory-name":"Supernova","user-attribute":"supern...@example.com"}, {"primary-key":"3","child-key":"5","date":"20150422","directory-name":"Transactional","user-attribute":"transactio...@transaction.org"}, {"primary-key":"4","child-key":"","date":"20150503","directory-name":"Spam","user-attribute":"allmys...@lovesspam.com"}, {"primary-key":"5","child-key":"","date":"20150506","directory-name":"Relational","user-attribute":"relatio...@transaction.org"}} SELECT directory-name FROM system WITH-IMPLICIT-JOIN WHERE-PK-IS-NOT-LINKED This would yield directory-name directory-name Bucket List Supernova Transactional Relational Spam Alternatively linking two user tables - profiles and contacts profiles PK-profiles user-name real-name age gender region contacts PK-contacts FK-profiles phone email icq home-page Getting the user-name and email would look something like: SELECT user-name, email FROM profiles WITH-IMPLICIT-JOIN When building our databases we already put a lot of work in normalising as much as we can. Then after all that work we have to virtually start again building up select, insert and update statements etc. all with all that referential integrity in mind. The advantages of a first class foreign key field as I see it are at least two fold. One it make building and maintaining your database easier. Two it is a means to provide some iterative structures easily coded. To me this looks like a good idea.
What happens if you have more then one child table with the same field? So: contacts FK-profiles .... email .... vendors FK-profiles .... email ....
-- Kind regards Stephen Feyrer
-- Adrian Klaver adrian.kla...@aklaver.com -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
