Manual views become stale when changes occur to their underlying base tables. Refreshing a manual view means that the database server re-executes the query definition for the view and replaces the view data with the new result set of the query. Refreshing makes the view data consistent with the underlying data. You should consider the acceptable degree of data staleness for the manual view and devise a refresh strategy. Your strategy should allow for the time it takes to complete a refresh, since the view is not available for querying during the refresh operation.

You can also set up a strategy in which the view is refreshed using events. For example, you can create an event to refresh at some regular interval.

Immediate views do not need to be refreshed except if they are uninitialized (contain no data), for example after being truncated.

You can also use the sa_refresh_materialized_views system procedure to refresh views. See sa_refresh_materialized_views system procedure.

You can configure a staleness threshold beyond which the optimizer should not use a materialized view when processing queries, using the materialized_view_optimization database option. See Setting the optimizer staleness threshold for materialized views.

When using the REFRESH MATERIALIZED VIEW statement, you can override the connection isolation level using the WITH ISOLATION LEVEL clause. For more information on how to control concurrency when refreshing a materialized view, see the WITH clause of the REFRESH MATERIALIZED VIEW statement.

 To refresh a manual view (Sybase Central)

 To refresh a manual view (SQL)

 Example

CREATE MATERIALIZED VIEW EmployeeConfid33 AS
   SELECT EmployeeID, Employees.DepartmentID, SocialSecurityNumber, Salary, ManagerID,
      Departments.DepartmentName, Departments.DepartmentHeadID
   FROM Employees, Departments
   WHERE Employees.DepartmentID=Departments.DepartmentID;
REFRESH MATERIALIZED VIEW EmployeeConfid33;

 See also