Re: enforcing uniqueness across tables

[Peter Brawley]

> equipment can only be in one place at one time

Depends on all the details of the business problem. but a common solution is for stock to be the main table, and define repair and customer tables as child tables eg

stock( sid int primary key, ... )
repair( rid int primary key, sid, date_in, date_out, foreign key(sid) references(stock), ... )
customer( cid int primary key, sid, date_rented, date_returned, foreign key(sid) references(stock), ... )