Re: multiple UNIQUE indices for FK

W dniu 28.02.2016 o 03:35, David G. Johnston pisze:
>     W dniu 23.02.2016 o 09:39, Rafal Pietrak pisze:
>     > Can anybody suggest any other way out of this mass?
> 
> 
> ​The only thought that sticks while reading your prose is:​
> 
> ​message ----> message-person <---- person​
>  
> 
> ​message-person (message_id, person_id, relationship_type[sender, 
> receiver])


It just occured to me: how do I make sure (e.g. force within a database) with the above structure, that a message can
have*only  one* sender?
 
but, allow for multiple recepients?

-R

____________________________________________________________________________________

If I'm not too late, unique partial index:

CREATE UNIQUE INDEX unique_message_sender (message_id, person_id) WHERE relationship_type = sender;



Regards,
Igor