Re: business users services

[Peter Brawley]

> the b_user column of the busers_services table will have the same value for 3 rows

The relational model tries to minimise redundant representation, not recurring real world data. What you describe is the latter, not the former. Not an issue.

> Two different B_users may offer the same service

Again, if you analyse such issues from Codd's relational the point of view, the most efficient way to represent such facts is to store keys that point to the data that recurs, which is what bridge tables like busers_services so efficiently do.

And whether you declare those keys Foreign Keys depends not on whether you "like" Foreign Keys, but rather on whether the requirement is that (i) the database engine enforce such constraints, which is usually more efficient, or (ii) application software do all such enforcement ensuring that buser_services column values point at existing user and service values.