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Microsoft SQL Server 2008 R2 Unleashed- P136

Microsoft SQL Server 2008 R2 Unleashed- P136:SQL Server 2005 provided a number of significant new features and enhancements over what was available in SQL Server 2000. This is not too surprising considering there was a five-year gap between these major releases.Microsoft SQL Server 2008 is not as much of a quantum leap forward from SQL Server 2005 | 1294 CHAPTER 35 Understanding Query Optimization sp_control_plan_guide N DROP1 N PlanGuidel1 To execute sp_control_plan_guide on a plan guide of type OBJECT for example a plan guide created for a stored procedure you must have at least ALTER permission on the object that is referenced by the plan guide. For all other plan guides you must have at least ALTER DATABASE permission. Attempting to drop or alter a function or stored procedure that is referenced by a plan guide results in an error. In SQL Server 2008 it is possible to define multiple plan guides for the same query. However only one plan guide can be active at a time. You can use sp_control_plan_guide to enable and disable plan guides. Validating Plan Guides The new system function sys.fn_validate_plan_guide can be used to validate a plan guide. Plan guides can become invalid after changes such as dropping an index are made to the physical design of the database. By validating a plan guide you can determine whether the plan guide can be used unmodified by the query optimizer. The sys.fn_validate_plan_guide function returns the first error message encountered when the plan guide is applied to its query. If the plan guide is valid an empty rowset is returned. The sys.plan_guides Catalog View All plan guides are stored in the sys.plan_guides database system catalog view. You can get information about the plan guides defined in a database by running a query against the sys.plan_guides catalog view as in the following example select name is_disabled scope_type_desc scope_object_id parameters hints query_text from sys.plan_guides Table 35.2 describes the columns in the sys.plan_guides catalog view. TABLE 35.2 sys.plan guides Columns Column Name Description plan_guide_id Unique identifier of the plan guide. Name Name of the plan guide. create_date Date and time the plan guide was created. modify_date Date the plan guide was last modified. is_disabled 1 disabled and 0 enabled. query_text Text of the query on which