In most cases it is wise to let SQL Server automatically update statistics.
To turn on automatic updates for all statistics in a database, if not already on, execute the following statement:
USE master
EXEC sp_dboption ‘MyDatabase’, ‘ auto update statistics’, ‘true’
To turn on automatic updates for all statistics on a specific table, such as Clients, execute the following statement:
USE MyDatabase
EXEC sp_autostats Clients, ‘ON’
To manually update the statistics on specific table, such as Clients, execute the following command:
USE MyDatabase
UPDATE STATISTICS Clients