For autoincrement fields: MAX(ID) vs TOP 1 ID ORDER BY ID DESC

Question

I want to find the highest AutoIncremented value from a field. (its not being fetched after an insert where I can use @@SCOPE_IDENTITY etc) Which of these two q

Answer 1

If there is a clustered index there is virtually no difference in performance between the two queries.

This is becuase both will perform a Clustered Index Scan that will bear 100% of the query cost.

Performing the two queries on a column that does not have an index results in 3 operators being used in both execution plans.

The Top clause uses the Sort operator and the Max function uses a Stream Aggregate operator.

When there is no index, the MAX() function provides better performance.

Proof of concept can be found and full walkthrough of a test scenario can be found here:

Performance Comparison Top 1 Verses MAX() Function