Which is Worse: an Unused Index, or an Un-Indexed Foreign Key? (Dear SQL DBA Episode 16)

Should you always index your foreign keys? What if you index your foreign key, and then the index never gets used?

[carstenhansen]

Another possibility is to add the foreign key the night before you need it - e.g. a yearly report and remove it afterwards.

[NancyMancarious]

Sometimes I wish that I work with you :)