In this case, the Query Optimizer might determine that using the index created for the view would result in the most efficient execution of this query. In addition to a database's physical design, the structure of the queries you use to save and retrieve data can also have a significant performance impact. Hardware problems such as insufficient memory or disk space can contribute to slow queries. However, poor query performance can be due to the Query Optimizer's inability to take advantage of indexes or statistical information. Tune-Up Checklist Click here .
Statistical information consists of information regarding the distribution of the data in a column.
The Query Optimizer uses statistical information to help determine the optimal way to execute a query. By default, the Auto Create Statistics database option in SQL Server is set to a value of True. This causes SQL Server to create statistical information automatically on additional columns in your tables as well. In addition to creating statistical information, SQL Server updates information periodically. How often it updates the information is determined by how often the data in the column or index changes and the volume of data in the column or index.