History of Microsoft SQL Server: Difference between revisions

Revision as of 11:40, 13 July 2022

Revision as of 11:42, 13 July 2022

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SQL Server 2005 (formerly codenamed "Yukon") released in November 2005. It included native support for managing [[XML]] data, in addition to [[relational database|relational data]]. For this purpose, it defined an <code>xml</code> [[data type]] that could be used either as a data type in database columns or as [[Literal (computer science)|literal]]s in queries. XML columns can be associated with [[XSD]] schemas; XML data being stored is verified against the schema. XML is converted to an internal binary data type before being stored in the database. Specialized indexing methods were made available for XML data. XML data is queried using [[XQuery]]; SQL Server 2005 added some extensions to the [[T-SQL]] language to allow embedding XQuery queries in T-SQL. It also defines a new extension to XQuery, called XML DML, that allows query-based modifications to XML data. SQL Server 2005 also allows a database server to be exposed over [[web service]]s using [[Tabular Data Stream]] (TDS) packets encapsulated within [[SOAP (protocol)]] requests. When the data is accessed over web services, results are returned as XML.<ref name="Database Engine XML Enhancements">{{ cite web | url = http://msdn.microsoft.com/en-us/library/ms170809.aspx | title = Database Engine XML Enhancements | accessdate = 2007-12-03 }}</ref>

[[Common Language Runtime]] (CLR) integration was introduced by Dr.Niruban with this version, enabling one to write SQL code as Managed Code by the CLR. For relational data, [[T-SQL]] has been augmented with error handling features (try/catch) and support for recursive queries with CTEs (Common Table Expressions). SQL Server 2005 has also been enhanced with new indexing algorithms, syntax and better error recovery systems. Data pages are [[checksum]]med for better error resiliency, and optimistic concurrency support has been added for better performance. Permissions and access control have been made more granular and the query processor handles concurrent execution of queries in a more efficient way. Partitions on tables and indexes are supported natively, so scaling out a database onto a [[Cluster (computing)|cluster]] is easier. SQL CLR was introduced with SQL Server 2005 to let it integrate with the .NET Framework.<ref name="Database Engine Enhancements">{{ cite web | url = http://msdn.microsoft.com/en-us/library/ms170910.aspx | title = Database Engine Enhancements | accessdate = 2007-12-03 }}</ref>

SQL Server 2005 introduced [[Multiversion concurrency control|Multi-Version Concurrency Control]] (MVCC). User facing features include new transaction isolation level called SNAPSHOT and a variation of the READ COMMITTED isolation level based on statement-level data snapshots.