History
Genesis.
Prior to version 7.0 the code base for MS SQL Server was sold by Sybase SQL Server to Microsoft, and was Microsoft's entry to the enterprise-level database market, competing against Oracle, IBM, and, later, Sybase. Microsoft, Sybase and Ashton-Tate originally worked together to create and market the first version named SQL Server 1.0 for OS/2 (about 1989) which was essentially the same as Sybase SQL Server 3.0 on Unix,VMS, etc. Microsoft SQL Server 4.2 was shipped around 1992 (available bundled with IBM OS/2 version 1.3). Later Microsoft SQL Server 4.21 for Windows NT was released at the same time as Windows NT 3.1. Microsoft SQL Server v6.0 was the first version designed for NT, and did not include any direction from Sybase.
About the time Windows NT was released in July 1993, Sybase and Microsoft parted ways and each pursued its own design and marketing schemes. Microsoft negotiated exclusive rights to all versions of SQL Server written for Microsoft operating systems. (In 1996 Sybase changed the name of its product to Adaptive Server Enterprise to avoid confusion with Microsoft SQL Server.) Until 1994, Microsoft's SQL Server carried three Sybase copyright notices as an indication of its origin.
SQL Server 7.0 and SQL Server 2000 included modifications and extensions to the Sybase code base, adding support for the IA-64 architecture. By SQL Server 2005 the legacy Sybase code had been completely rewritten. Since the release of SQL Server 2000, advances have been made in performance, the client IDE tools, and several complementary systems that are packaged with SQL Server 2005. These include:
- an extract-transform-load (ETL) tool (SQL Server Integration Services or SSIS)
- a Reporting Server
- an OLAP and data mining server (Analysis Services)
- several messaging technologies, specifically Service Broker and Notification Services
SQL Server 2005
SQL Server 2005 (formerly code named "Yukon") released in October 2005. It included native support for managing XML data, in addition to relational data. For this purpose, it defined an
xml data type that could be used either as a data type in database columns or as literals 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. In addition, 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 services using Tabular Data Stream (TDS) packets encapsulated within SOAP (protocol)requests. When the data is accessed over web services, results are returned as XML.
Common Language Runtime (CLR) integration was introduced 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 check summed 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 naively, so scaling out a database onto a cluster is easier. SQL CLR was introduced with SQL Server 2005 to let it integrate with the .NET Framework.SQL Server 2005 introduced Multi-Version Concurrency Control. 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.
SQL Server 2005 introduced "MARS" (Multiple Active Results Sets), a method of allowing usage of database connections for multiple purposes.
SQL Server 2005 introduced DMVs (Dynamic Management Views), which are specialized views and functions that return server state information that can be used to monitor the health of a server instance, diagnose problems, and tune performance.
Service Pack 1 (SP1) of SQL Server 2005 introduced Database Mirroring, a high availability option that provides redundancy and failover capabilities at the database level. Failover can be performed manually or can be configured for automatic failover. Automatic failover requires a witness partner and an operating mode of synchronous (also known as high-safety or full safety).