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

I've just tested the two SQL statements you provided against a typical dataset:

SELECT MAX(Id) FROM Table1

SELECT TOP 1 Id FROM Table1 ORDER BY Id DESC

And SELECT TOP 1 Id FROM Table1 ORDER BY Id DESC is marginally faster because it has one fewer step in the execution plan. Here are the execution plans each query carries out:

SELECT MAX(Id) FROM Table1

Clustered Index Scan >> Top >> Stream Aggregate >> Select

SELECT TOP 1 Id FROM Table1 ORDER BY Id DESC

Clustered Index Scan >> Top >> Select