. . . of clauses or functions that might be used in SQL statements or FOR clauses.

Any (SQL) clause (or whatever it may be [predicate?]) or function that is candidate should have its applicability to optimization clearly noted. This would include things like:
- BETWEEN and NOT BETWEEN
- BETWEEN() and NOT BETWEEN()
- LIKE and NOT LIKE
- LIKE() and NOT LIKE()
- ALL (per example #3 in SQL - Select command reference entry)
- ANY and SOME (per example #4 in SQL - Select command reference entry)
- EXISTS and NOT EXISTS
- IN and NOT IN
- INLIST() and NOT INLIST()
- EMPTY() and NOT EMPTY()
- $ operator

Basically any function should have a sub-heading for "Optimizable" and should state yes or no, also describing special conditions if applicable.
The SQL 'clauses' (predicates?) should each note this too. Unfortunately, many have only an example as their 'description' and it would be vry helpful if this was addressed too.