Discussion: What are the advantages/disadvantages to combination k

Hi everyone,

I'm interested in hearing the opinions of people who use (or choose not to
use) combination keys in their table structure. What do you think the
advantages and disadvantages of using combination keys are?

If I were to have these tables:

tblMainTopic
MainID

tblSubTopic
SubID

Then I have two options for relating the two above tables in a junction table.

Option I:

tblManyToMany
MainID { These two foreign keys
SubID { are joined as a combination key

Option II:

tblManyToMany
m2mID 'auto-number primary
MainID 'foreign key
SubID 'foreign key

Thanks to all who take the time to post their opinions.

--
rpw