SQL Server 2014 Improves Query Performance, Security, Stability

SQL Server 2014 includes several changes and new features, which should benefit organizations that manage complex and large databases or have strong security and audit requirements. Updates to the database engine improve overall performance and new management features provide greater database stability and security; however, existing databases require thorough testing prior to migration, and some performance options may introduce risk of data loss.

Query Performance Improvements

A recurring theme in SQL Server updates is to deliver performance improvements that address the increasing volume of data in most organizations. Several changes in SQL Server 2014 that provide performance improvements include the following:

Query optimizer overhaul. The query optimizer, which had received few changes since SQL Server 7.0, is the planning tool within the SQL Server engine that analyzes a query and generates an optimized plan for execution. For example, a query that selects data from two tables and filters the results may have an optimized plan (calculated by a part of the optimizer called the Cardinality Estimator) that first selects indexes on one table to find and filter the data, prior to joining those results to a second table. SQL Server 2014 introduces significant changes that should improve query performance for most existing applications and databases, but may cause degraded performance for queries on older databases. Tuning options for degraded queries include deactivating the new Cardinality Estimator in favor of the older version, and can be applied to individual databases.