Updating a large table is a common scenario. This is often encountered in cases of applications that performs series of tasks in the background or data warehousing loading scenarios. To reduce locking and logging resources, such update statements are broken down into smaller batches or units of work. This has been traditionally done using SET ROWCOUNT setting in SQL Server. Now, SQL Server 2005 provides you with a simpler construct that the optimizer can understand and use efficiently. TOP clause has been enhanced in SQL Server 2005 to support expressions and can be used now in all DML operations. Let's look at a quick example on how to use TOP with UPDATE:
SQL Server Engine Tips : SQL Server 2005
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