A question for people re performance.

As I said above, we use a date table, and as our significant dates are of type [date] (with no time-of-day), we can join ON a.Datefield = b.Datefield, which is fast.

However, some new data will use [datetime] fields, where the time of day is not 00:00:00. We can match using BETWEEN or CONVERT(DATE,a.Datefield), but is that going to slow down the join? Should we add computed or pre-computed fields of type [date] to use in joins, or would this not gain anything? (Assume all fields being joined on are indexed.)