title: SQL Server Hash Indexes
body: <p>When using the CHECKSUM column type to artificially create a hash index, is the lookup actually O(1) or is it still O(lg n) like it is for a clustered index? I have a table from which I will select based on its ID column and I need the lookup to be as fast as possible, so is the clustered index the fastest possible option? I am looking for something that will provide O(1) performance.</p>