Is an index on A, B redundant if there is an index on A, B, C?

Question

Having years of experience as a DBA, I do believe I know the answer to the question, but I figured it never hurts to check my bases.

Using SQL Server, assuming I have a

Answer 1

I typically would find this "almost" similar index in table that contains historical data. If column C is a date or integer column, be careful. It is most likely used to satisfy the MAX function as in WHERE tblA.C = MAX(tblB.C), which skips the table altogether and utilize an index only access path.