I've read (and lost the reference) that when doing joins
of this form:

A.col = B.col and A.col = C.col

It is "helpful" to explicitlty add the
implied join:

B.col = C.col

This is mathematically redundant, but may give
the SQL optimiser another (potentially useful/fast)
option.

Can anybody comment, (or remember where I might
have seen this tip)?

BugBear