Re: Join tables in MySQL

David, thank you very much, that's very informative!

Indeed my issue is with Scenario 2, where I have additional
attributes.  I still want to do the equivalent of using flattened
relationships (why the prohibition?) without doing extra work - I
would be able to do that in a low-level SQL based system.

If I have a TermCon which has two relationships (equiv to FK) to
Entity1 & Entity2, I want to be able to generate a list (e.g. NSArray)
of related Entity2s to Entity1, something like Entity1.entity2s().

However, there is no such flattened relationship, so it looks like I
have to
a) use Entity1.TermCons() to fill an NSArray and then
b) loop through this to select related TermCon.Entity2() to fill a new
NSMutableArray, checking to ensure uniqueness.

This results in an array of all the Entity2s related to a particular
Entity1.

This is entirely doable but it's all in code, which surely defeats the
advantage of using WO relationships.  Hence I thought there must be
some way of explicitly creating a 'Join Table' entity and using the
flattened relationships, hence the desire to create rows in a dual-PK
table, or at least the WO high-level equivalent.

At the DB level, the TermCon table only needs one PK, as the 2
entiities are mapped by 2 FKs, all eo_pk_table friendly.

However, thinking low-level for a moment, why can't I use an explicit
dual-PK table and have WO make sue of flattened relationships, or even
use FK-flattening through a single-PK table?

Is this the way things are, or am I missing something?


John







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