多对多无联接表

Question

I have a Template and Comment table.

Template has two fields ID and KEY , I can have multiple versions of a template with the same KEY but different ID . For example:

ID   1  2  3
KEY  1  1  1

And a Comment table with a ID column:

ID             1  2  3
TEMPLATE_KEY   1  1  1

Is it possible to do a many-to-many between Template and Comment like Template(key) <-> Comment(ID) without a join table ?

Answer 1

ManyToMany is never possible without an additional table in a relational database. Why would one want to avoid such a table at all?

Answer 2

It is possible to do this but a join table will make referential integrity reasonable to enforce. You could store foreign key arrays on both sides, code triggers to manage them, and the like and if you do a delete, you will have a lot of proboems.....

Now, it is possible that in 9.4, this will be natively supported but it isn't there yet and the patches are still under discussion. In general though, usually it is better to just go through join tables.