Learn the ins and out of updating
Server updates rows in multiple ways, automatically and invisibly choosing the fastest update strategy for a specific operation. In determining the strategy, SQL Server evaluates the number of affected rows, how it will access the rows (by a scan or an index retrieval, and through which index), and whether changes to the index keys will occur. In SQL Server 7.0, updates can happen in place or as a delete followed by an insert. (An in-pl...