Microsoft SQL Server
Developed by	Microsoft
Latest release	SQL Server 2008 / June, 2008
OS	Microsoft Windows
Genre	RDBMS
License	Microsoft EULA
Website	http://www.microsoft.com/sqlserver/2008/en/us/default.aspx

Microsoft SQL Server is a relational database management system (RDBMS) produced by Microsoft. A software developer is a person or organization concerned with facets of the software development process wider than design and coding a somewhat broader scope of Microsoft Corporation is an American multinational Computer technology Corporation, which rose to dominate the Home computer A software release is the distribution whether public or private of an initial or new and upgraded version of a Computer software product Events in June Madaraka Day June 1 to commemorate when Kenya gained internal self-rule 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common An operating system (commonly abbreviated OS and O/S) is the software component of a Computer system that is responsible for the management and coordination Microsoft Windows is a series of Software Operating systems and Graphical user interfaces produced by Microsoft. Computer software can be organized into categories based on common function type or field of use A Relational database management system (RDBMS is a Database management system (DBMS that is based on the Relational model as introduced by E A software license (or software licence in commonwealth usage is a Legal instrument governing the usage or redistribution of copyright protected software A website (alternatively web site or Web site, a back-construction from the Proper noun World Wide Web) is a collection of Web pages A Relational database management system (RDBMS is a Database management system (DBMS that is based on the Relational model as introduced by E Microsoft Corporation is an American multinational Computer technology Corporation, which rose to dominate the Home computer Its primary query language is Transact-SQL, an implementation of the ANSI/ISO standard Structured Query Language (SQL) used by both Microsoft and Sybase. Query languages are Computer languages used to make queries into Databases and Information systems Broadly query languages can be classified Transact-SQL ( T-SQL) is Microsoft 's and Sybase 's proprietary extension to the SQL. Sybase Inc ( is an enterprise software and services company exclusively focused on managing and mobilizing information

Architecture

The architecture of Microsoft SQL Server is broadly divided into three components: SQLOS which implements the basic services required by SQL Server, including thread scheduling, memory management and I/O management; the Relational Engine, which implements the relational database components including support for databases, tables, queries and stored procedures as well as implementing the type system; and the Protocol Layer which exposes the SQL Server functionality. ^[1]

SQLOS

SQLOS is the base component in the SQL Server architecture. It implements functions normally associated with the Operating System - thread scheduling, memory management, I/O management, buffer pool management, resource management, synchronization primitives and locking, and deadlock detection. Because the requirement of SQL Server is highly specialized,^[1] SQL Server implements its own memory and thread management system, rather than using the generic one already implemented in the operating system. It divides all the operations it performs into a series of Tasks - both background maintenance jobs as well as processing requests from clients. ^[2] Internally, a pool of worker threads is maintained, onto which the tasks are scheduled. A task is associated with the thread until it is completed, only after its completion is the thread freed and returned to the pool. If there are no free threads to assign the task to, the task is temporarily blocked. ^[2] Each worker thread is mapped onto either an Operating System thread or a fiber. A thread in Computer science is short for a thread of execution. Fibers are user mode threads that implement co-operative multitasking. "kernel space" redirects here For mathematical definition see Null space. In computing Multitasking is a method by which multiple tasks also known as processes, share common processing resources such as a CPU. Using fibers means SQLOS does all the book-keeping of thread management itself, but then it can optimize them for its particular use. ^[2] SQLOS also includes synchronization primitives for locking as well as monitoring for the worker threads to detect and recover from deadlocks. A lock is used when multiple users need to access a Database concurrently. A deadlock is a situation wherein two or more competing actions are waiting for the other to finish and thus neither ever does ^[1]

SQLOS handles the memory requirements of SQL Server as well. Reducing disc I/O is one of the primary goals of specialized memory management in SQL Server. ^[3] It maintains a buffer pool, which is used to cache data pages from the disc, and to satisfy the memory requirements for the query processor, and for other internal data structures. In Computer science, a cache (kæʃ like "cash") is a collection of data duplicating original ^[1] SQLOS monitors all the memory allocated from the buffer pool, ensuring that the components return unused memory to the pool, and shuffles data out of the cache to make room for newer data. For changes that are made to the data in buffer, SQLOS writes the data back to the disc lazily, that is when the disc subsystem is either free, or there have significant number of changes made to the cache, while still serving requests from the cache. For this, it implements a Lazy Writer, which handles the task of writing the data back to persistent storage. ^[1]

SQL Server normally supports up to 2 GB memory on x86 hardware, though it can be configured to use up to 64 GB if the Address Windowing Extension is used in the supporting operating system. See also X86 assembly language The generic term x86 refers to the most commercially successful Instruction set architecture in the history of Personal Address Windowing Extensions (AWE is a Microsoft Windows Application Programming Interface that allows a 32-bit software application to access more For x64 hardware, it supports 8 TB of memory, and 7 TB for IA-64 systems (currently it is limited by Windows Server 2003 SP1 to 1TB). x86-64 is a Superset of the x86 instruction set architecture. Itanium is the brand name for 64-bit Intel Microprocessors that implement the Intel Itanium architecture (formerly called IA-64) However, when running x86 versions of SQL Server on x64 hardware, it can access 4 GB of memory without any special configuration. See also X86 assembly language The generic term x86 refers to the most commercially successful Instruction set architecture in the history of Personal x86-64 is a Superset of the x86 instruction set architecture. ^[3]

Relational engine

The Relational engine implements the relational data store using the capabilities provided by SQLOS, which is exposed to this layer via the private SQLOS API. A relational database is a Database that groups data using common attributes found in the data set It implements the type system, to define the types of the data that can be stored in the tables, as well as the different types of data items (such as tables, indexes, logs etc) that can be stored. It includes the Storage Engine, which handles the way data is stored on persistent storage devices and provides methods for fast access to the data. The storage engine implements log-based transaction to ensure that any changes to the data are ACID compliant. Data logging is the practice of recording sequential Data, often chronologically. A database transaction is a unit of work performed against a Database management system or similar system that is treated in a coherent and reliable way independent of other In Computer science, ACID ( Atomicity Consistency Isolation Durability) is a set of properties that guarantee that Database transactions are It also includes the query processor, which is the component that retrieves data. SQL queries specify what data to retrieve, and the query processor optimizes and translates the query into the sequence of operations needed to retrieve the data. The operations are then performed by worker threads, which are scheduled for execution by SQLOS. ^[1]

Protocol layer

Protocol layer implements the external interface to SQL Server. All operations that can be invoked on SQL Server are communicated to it via a Microsoft-defined format, called Tabular Data Stream (TDS). Tabular Data Stream ( TDS) is an Application layer protocol, used to transfer data between a Database server and a client Tabular Data Stream (TDS) is an application layer protocol, used to transfer data between a database server and a client. Initially designed and developed by Sybase Inc. for their Sybase SQL Server relational database engine in 1984, and later by Microsoft in Microsoft SQL Server. Adaptive Server Enterprise (ASE is Sybase Corporation's flagship enterprise-class Relational database management system product TDS packets can be encased in other physical transport dependent protocols, including TCP/IP, Named pipes, and Shared memory. The Internet Protocol Suite (commonly TCP/IP) is the set of Communications protocols used for the Internet and other similar networks In Computing, a named pipe (also FIFO for its behaviour is an extension to the traditional pipe concept on Unix and Unix-like In Computing, shared memory is a memory that may be simultaneously accessed by multiple programs with an intent to provide communication among them or avoid redundant copies Consequently, access to SQL Server is available over these protocols. In addition, the SQL Server API is also exposed over web services. A Web service (also Web Service) is defined by the W3C as "a software system designed to support interoperable machine-to-machine interaction ^[1]

Data storage

The main unit of data storage is a database, which is a collection of tables with typed columns. A Computer Database is a structured collection of records or data that is stored in a computer system In Computer science, a type system defines how a Programming language classifies values and expressions into '''types''', how it can SQL Server supports different data types, including primary types such as Integer, Float, Decimal, Char (including character strings), Varchar (variable length character strings), binary (for unstructured blobs of data), Text (for textual data) among others. In Computer science, primitive types — as distinct from Composite types ' — are Data types provided by a Programming language as basic A binary large object, also known as a blob, is a collection of Binary data stored as a single entity in a Database management system. It also allows user-defined composite types (UDTs) to be defined and used. SQL Server also makes server statistics available as virtual tables and views (called Dynamic Management Views or DMVs). A database can also contain other objects including views, stored procedures, indexes and constraints, in addition to tables, along with a transaction log. In Database theory, a view is a stored query accessible as a virtual table composed of the result set of a query. A stored procedure is a Subroutine available to applications accessing a relational database system. A database index is a Data structure that improves the speed of operations on a database table. A relational database is a Database that groups data using common attributes found in the data set An SQL Server database can contain a maximum of 2³¹ objects, and can span multiple OS-level files with a maximum file size of 2²⁰ TB. A terabyte (derived from the prefix Tera- and commonly abbreviated TB) is a measurement term for data storage capacity. ^[1] The data in the database are stored in primary data files with an extension . mdf. Secondary data files, identified with an . ndf extension, are used to store optional metadata. Log files are identified with the . ldf extension. ^[1]

Storage space allocated to a database is divided into sequentially numbered pages, each 8 KB in size. A page is the basic unit of I/O for SQL Server operations. A page is marked with a 96-byte header which stores metadata about the page including the page number, page type, free space on the page and the ID of the object that owns it. Page type defines the data contained in the page - data stored in the database, index, allocation map which holds information about how pages are allocated to tables and indexes, change map which holds information about the changes made to other pages since last backup or logging, or contain large data types such as image or text. While page is the basic unit of an I/O operation, space is actually managed in terms of an extent which consists of 8 pages. A database object can either span all 8 pages in an extent ("uniform extent") or share an extent with up to 7 more objects ("mixed extent"). A row in a database table cannot span more than one page, so is limited to 8 KB in size. However, if the data exceeds 8 KB and the row contains Varchar or Varbinary data, the data in those columns are moved to a new page (or possible a sequence of pages, called Allocation unit) and replaced with a pointer to the data. ^[4]

For physical storage of a table, its rows are divided into a series of partitions (numbered 1 to n). The partition size is user defined; by default all rows are in a single partition. A table is split into multiple partitions in order to spread a database over a cluster. Rows in each partition are stored in either B-tree or heap structure. In Computer science, a B-tree is a Tree data structure that keeps data sorted and allows searches insertions and deletions in logarithmic amortized In Computer science, a heap is a specialized tree -based Data structure that satisfies the heap property if B is a If the table has an associated index to allow fast retrieval of rows, the rows are stored in-order according to their index values, with a B-tree providing the index. A database index is a Data structure that improves the speed of operations on a database table. The data is in the leaf node of the leaves, and other nodes storing the index values for the leaf data reachable from the respective nodes. If the index is non-clustered, the rows are not sorted according to the index keys. An indexed view has the same storage structure as an indexed table. In Database theory, a view is a stored query accessible as a virtual table composed of the result set of a query. A table without an index is stored in an unordered heap structure. Both heaps and B-trees can span multiple allocation units. ^[5]

Buffer management

SQL Server buffers pages in RAM to minimize disc I/O. Any 8 KB page can be buffered in-memory, and the set of all pages currently buffered is called the buffer cache. The amount of memory available to SQL Server decides how many pages will be cached in memory. The buffer cache is managed by the Buffer Manager. Either reading from or writing to any page copies it to the buffer cache. Subsequent reads or writes are redirected to the in-memory copy, rather than the on-disc version. The page is updated on the disc by the Buffer Manager only if the in-memory cache has not been referenced for some time. While writing pages back to disc, asynchronous I/O is used whereby the I/O operation is done in a background thread so that other operations do not have to wait for the I/O operation to complete. Each page is written along with its checksum when it is written. A checksum is a form of Redundancy check, a simple way to protect the integrity of data by detecting errors in data that are sent through space ( Telecommunications When reading the page back, its checksum is computed again and matched with the stored version to ensure the page has not been damaged or tampered with in the mean time. ^[6]

Logging and Transaction

SQL Server ensures that any change to the data is ACID-compliant, i. In Computer science, ACID ( Atomicity Consistency Isolation Durability) is a set of properties that guarantee that Database transactions are e. , it uses transactions to ensure that any operation either totally completes or is undone if fails, but never leave the database in an intermediate state. A database transaction is a unit of work performed against a Database management system or similar system that is treated in a coherent and reliable way independent of other Using transactions, a sequence of actions can be grouped together, with the guarantee that either all actions will succeed or none will. SQL Server implements transactions using a write-ahead log. Any changes made to any page will update the in-memory cache of the page, simultaneously all the operations performed will be written to a log, along with the transaction ID which the operation was a part of. Each log entry is identified by an increasing Log Sequence Number (LSN) which ensure that no event overwrites another. SQL Server ensures that the log will be written onto the disc before the actual page is written back. This enables SQL Server to ensure integrity of the data, even if the system fails. If both the log and the page were written before the failure, the entire data is on persistent storage and integrity is ensured. If only the log was written (the page was either not written or not written completely), then the actions can be read from the log and repeated to restore integrity. If the log wasn't written, then also the integrity is maintained, even though the database is in a state when the transaction as if never occurred. If it was only partially written, then the actions associated with the unfinished transaction are discarded. Since the log was only partially written, the page is guaranteed to have not been written, again ensuring data integrity. Removing the unfinished log entries effectively undoes the transaction. SQL Server ensures consistency between the log and the data every time an instance is restarted. ^[1]

Concurrency and locking

SQL Server allows multiple clients to use the same database concurrently. As such, it needs to control concurrent access to shared data, to ensure data integrity - when multiple clients update the same data, or clients attempt to read data that is in the process of being changed by another client. SQL Server provides two modes of concurrency control: pessimistic concurrency and optimistic concurrency. When pessimistic concurrency control is being used, SQL Server controls concurrent access by using locks. Locks can be either shared or exclusive. Exclusive lock grants the user exclusive access to the data - no other user can access the data as long as the lock is held. Shared locks are used when some data is being read - multiple users can read from data locked with a shared lock, but not acquire an exclusive lock. The latter would have to wait for all shared locks to be released. Locks can be applied on different levels of granularity - on entire tables, pages, or even on a per-row basis on tables. For indexes, it can either be on the entire index or on index leaves. The level of granularity to be used is defined on a per-database basis by the database administrator. While a fine grained locking system allows more users to use the table or index simultaneously, it requires more resources. So it does not automatically turn into higher performing solution. SQL Server also includes two more lightweight mutual exclusion solutions - latches and spinlocks - which are less robust than locks but are less resource intensive. Mutual exclusion (often abbreviated to mutex) Algorithms are used in Concurrent programming to avoid the simultaneous use of a common resource such as a SQL Server uses them for DMVs and other resources that are usually not busy. SQL Server also monitors all worker threads that acquire locks to ensure that they do not end up in deadlocks - in case they do, SQL Server takes remedial measures, which in many cases is to kill one of the threads entangled in a deadlock and rollback the transaction it started. A deadlock is a situation wherein two or more competing actions are waiting for the other to finish and thus neither ever does ^[1] To implement locking, SQL Server contains the Lock Manager. The Lock Manager maintains an in-memory table that manages the database objects and locks, if any, on them along with other metadata about the lock. Access to any shared object is mediated by the lock manager, which either grants access to the resource or blocks it.

SQL Server also provides the optimistic concurrency control mechanism, which is similar to the multiversion concurrency control used in other databases. Multiversion concurrency control (abbreviated MCC or MVCC) in the Database field of Computer science, is a Concurrency control The mechanism allows a new version of a row to be created whenever the row is updated, as opposed to overwriting the row, i. e. , a row is additionally identified by the ID of the transaction that created the version of the row. Both the old as well as the new versions of the row are stored and maintained, though the old versions are moved out of the database into a system database identified as Tempdb. When a row is in the process of being updated, any other requests are not blocked (unlike locking) but are executed on the older version of the row. If the other request is an update statement, it will result in two different versions of the rows - both of them will be stored by the database, identified by their respective transaction IDs. ^[1]

Data retrieval

The main mode of retrieving data from an SQL Server database is querying for it. A Computer Database is a structured collection of records or data that is stored in a computer system The query is expressed using a variant of SQL called T-SQL, a dialect Microsoft SQL Server shares with Sybase SQL Server due to its legacy. Transact-SQL ( T-SQL) is Microsoft 's and Sybase 's proprietary extension to the SQL. Adaptive Server Enterprise (ASE is Sybase Corporation's flagship enterprise-class Relational database management system product The query declaratively specifies what is to be retrieved. It is processed by the query processor, which figures out the sequence of steps that will be necessary to retrieve the requested data. The sequence of actions necessary to execute a query is called a query plan. There might be multiple ways to process the same query. For example, for a query that contains a join statement and a select statement, executing join on both the tables and then executing select on the results would give the same result as selecting from each table and then executing the join, but result in different execution plans. A SQL JOIN clause combines records from two tables in a Relational database, resulting in a new temporary table sometimes called a "joined table" A SQL SELECT statement returns a Result set of records from one or more tables In such case, SQL Server chooses the plan that is supposed to yield the results in the shortest possible time. This is called query optimization and is performed by the query processor itself. Query optimization is a function of many Relational database management systems in which multiple Query plans for satisfying a query are examined and a good Query ^[1]

SQL Server includes a cost-based query optimizer which tries to optimize on the cost, in terms of the resources it will take to execute the query. Given a query, the query optimizer looks at the database schema, the database statistics and the system load at that time. The schema (pronounced skee -ma) of a Database system is its structure described in a formal language supported by the Database management system It then decides which sequence to access the tables referred in the query, which sequence to execute the operations and what access method to be used to access the tables. For example, if the table has an associated index, whether the index should be used or not - if the index is on a column which is not unique for most of the columns (low "selectivity"), it might not be worthwhile to use the index to access the data. Finally, it decides whether to execute the query concurrently or not. Concurrent computing is the concurrent (simultaneous execution of multiple interacting computational tasks While a concurrent execution is more costly in terms of total processor time, because the execution is actually split to different processors might mean it will execute faster. Once a query plan is generated for a query, it is temporarily cached. For further invocations of the same query, the cached plan is used. Unused plans are discarded after some time. ^[1][7]

SQL Server also allows stored procedures to be defined. A stored procedure is a Subroutine available to applications accessing a relational database system. Stored procedures are parameterized T-SQL queries, that are stored in the server itself (and not issued by the client application as is the case with general queries). Stored procedures can accept values sent by the client as input parameters, and send back results as output parameters. They can also call other stored procedures, and can be selectively provided access to. Access control is the ability to permit or deny the use of a particular resource by a particular entity Unlike other queries, stored procedures have an associated name, which is used at runtime to resolve into the actual queries. Also because the code need not be sent from the client every time (as it can be accessed by name), it reduces network traffic and somewhat improves performance. ^[8] Execution plans for stored procedures are also cached as necessary.

SQL CLR

Main article: SQL CLR

Microsoft SQL Server 2005 includes a component named SQL CLR via which it integrates with .NET Framework. SQL CLR or SQLCLR ( SQL Common Language Runtime) is technology for hosting of the Microsoft. Unlike most other applications that leverage .NET Framework functionality, SQL Server itself hosts the .NET Framework runtime, i. The Common Language Runtime (CLR is the Virtual machine component of Microsoft's. e. , memory, threading and resource management requirements of . NET Framework are satisfied by SQLOS itself, rather than the underlying Windows operating system. SQLOS provides deadlock detection and resolution services for . NET code as well. With SQL CLR, stored procedures and triggers can be written in any managed .NET language, including C# and VB.NET. A stored procedure is a Subroutine available to applications accessing a relational database system. A database trigger is Procedural code that is automatically executed in response to certain events on a particular table in a Database. Managed code is computer program code that executes under the management of a Virtual machine, unlike unmanaged code which is executed directly by the computer's C# (pronounced C Sharp is a Multi-paradigm Visual Basic.NET ( VBNET) is an object-oriented Computer language that can be viewed as an evolution of Microsoft's Visual Basic Managed code can also be used to define UDTs which can be persisted in the database. Managed code is computer program code that executes under the management of a Virtual machine, unlike unmanaged code which is executed directly by the computer's In Computer science, object composition (not to be confused with function composition) is a way and practice to combine simple objects or Managed code is compiled to .NET assemblies and after being verified for type safety, registered at the database. Managed code is computer program code that executes under the management of a Virtual machine, unlike unmanaged code which is executed directly by the computer's In Computer science, type safety is a property of some Programming languages that is defined differently by different communities but most definitions involve After that, they can be invoked like any other procedure. ^[9] However, only a subset of the Base Class Library is available, when running code under SQL CLR. The Base Class Library ( BCL) is a Standard library available to all languages using the. Most APIs relating to user interface functionality are not available. The user interface (or Human Computer Interface) is the aggregate of means by which people&mdash the users '&mdash interact with the System ^[9]

When writing code for SQL CLR, data stored in SQL Server databases can be accessed using the ADO.NET APIs like any other managed application that accesses SQL Server data. ADONET is a set of computer software components that can be used by programmers to access data and data services Managed code is computer program code that executes under the management of a Virtual machine, unlike unmanaged code which is executed directly by the computer's However, doing that creates a new database session, different from the one in which the code is executing. To avoid this, SQL Server provides some enhancements to the ADO.NET provider that allows the connection to be redirected to the same session which already hosts the running code. ADONET is a set of computer software components that can be used by programmers to access data and data services Such connections are called context connections and are set by setting context connection parameter to true in the connection string. SQL Server also provides several other enhancements to the ADO.NET API, including classes to work with tabular data or a single row of data as well as classes to work with internal metadata about the data stored in the database. ADONET is a set of computer software components that can be used by programmers to access data and data services It also provides access to the XML features in SQL Server, including XQuery support. XQuery is a Query language (with some Programming language features that is designed to query collections of XML data These enhancements are available only when running code under SQL CLR, and not available generally. ^[10][11]

Services

SQL Server also includes an assortment of add-on services. While these are not essential for the operation for the database system, these provide value added services on top of the core database management system. These services either run as a part of some SQL Server component or out-of-process as Windows Service and presents their own API to control and interact with them. On Microsoft Windows Operating systems a Windows service is a long-running executable that performs specific functions and which is designed not to require user intervention

Service Broker

The Service Broker, which runs as a part of the database engine, provides a reliable messaging and message queuing platform for SQL Server applications. In Computer science, a message queue is a software-engineering component used for Interprocess communication or inter- thread communication Used inside an instance, it is used to provide an asynchronous programming environment. For cross instance applications, Service Broker communicates over TCP/IP and allows the different components to be synchronized together, via exchange of messages. The Internet Protocol Suite (commonly TCP/IP) is the set of Communications protocols used for the Internet and other similar networks ^[12]

Replication Services

SQL Server Replication Services are used by SQL Server to replicate and synchronize database objects, either in entirety or a subset of the objects present, across replication agents, which might be other database servers across the network, or database caches on the client side. Replication follows a publisher/subscriber model, i. e. , the changes are sent out by one database server ("publisher") and are received by others ("subscribers"). SQL Server supports three different types of replication:^[13]

Transaction replication

Each transaction made to the publisher database (master database) is synced out to subscribers, who update their databases with the transaction. Transactional replication synchronizes databases in near real time. ^[14]

Merge replication

Changes made at both the publisher and subscriber databases are tracked, and periodically the changes are synchronized bi-directionally between the publisher and the subscribers. If the same data has been modified differently in both the publisher and the subscriber databases, synchronization will result in a conflict which has to be resolved - either manually or by using pre-defined policies. ^[15]

Snapshot replication

Snapshot replication published a copy of the entire database (the then-snapshot of the data) and replicates out to the subscribers. Further changes to the snapshot are not tracked. ^[16]

Analysis Services

Main article: SQL Server Analysis Services

SQL Server Analysis Services adds OLAP and data mining capabilities for SQL Server databases. Microsoft Analysis Services is a group of OLAP and Data Mining services provided in Microsoft SQL Server. Online Analytical Processing or OLAP (ˈoʊlæp is an approach to quickly provide answers to analytical queries that are multi-dimensional in nature Data mining is the process of Sorting through large amounts of data and picking out relevant information The OLAP engine supports MOLAP, ROLAP and HOLAP storage modes for data. MOLAP stands for M ultidimensional O ROLAP stands for R elational O n' HOLAP ( H ybrid O n' l' ine A nalytical P rocessing is a combination of ROLAP and MOLAP which are other possible implementation Analysis Services supports the XML for Analysis standard as the underlying communication protocol. XML for Analysis (abbreviated as XMLA) is the industry standard for data access in analytical systems such as OLAP and Data Mining. The cube data can be accessed using MDX queries. Multidimensional Expressions (MDX is a Query language for OLAP Databases much like SQL is a query language for Relational databases ^[17] Data mining specific functionality is exposed via the DMX query language. Data Mining Extensions (DMX is a query language for Data Mining Models much like SQL is a query language for Relational databases and MDX is Analysis Services includes various algorithms - Decision trees, clustering algorithm, Naive Bayes algorithm, time series analysis, sequence clustering algorithm, linear and logistic regression analysis, and neural networks - for use in data mining. In Operations research, specifically in Decision analysis, a decision tree (or tree diagram is a decision support tool that uses a graph or A naive Bayes classifier is a simple probabilistic classifier based on applying Bayes' theorem with strong (naive independence assumptions Traditionally the term neural network had been used to refer to a network or circuit of biological neurons. ^[18]

Reporting Services

Main article: SQL Server Reporting Services

SQL Server Reporting Services is a report generation environment for data gathered from SQL Server databases. SQL Server Reporting Services (SSRS is a server-based report generation software system from Microsoft. It is administered via a web interface. The World Wide Web (commonly shortened to the Web) is a system of interlinked Hypertext documents accessed via the Internet. Reporting services features a web services interface to support the development of custom reporting applications. A Web service (also Web Service) is defined by the W3C as "a software system designed to support interoperable machine-to-machine interaction Reports are created as RDL files. Report Definition Language (RDL is a standard proposed by Microsoft for defining reports ^[19]

Reports can be designed using recent versions of Microsoft Visual Studio(including Visual Studio. Microsoft Visual Studio is the main Integrated Development Environment (IDE from Microsoft. NET 2003 onwards) with Business Intelligence Development Studio, installed or with the included Report Builder. Business Intelligence Development Studio ( BIDS) is the IDE from Microsoft used for developing data analysis and Business Intelligence solutions Once created, RDL files can be rendered in a variety of formats^[20] including Excel, PDF, CSV, XML, TIFF (and other image formats)^[21], and HTML Web Archive. The comma separated list (CSL is a Data Format originally known as comma-separated values (CSV in the oldest days of simple computers Don't change "Extensible"

Notification Services

Main article: SQL Server Notification Services

SQL Server Notification Services is a platform for generating notifications, which are sent to Notification Services subscribers. SQL Server Notification Services is being Removed from SQL Server 2008 Notification Services is based on SQL Server Technology, and sits atop the Microsoft A subscriber registers for a specific event or transaction (which is registered on the database server as a trigger); when the event occurs, Notification Services uses Service Broker to send a message to the subscriber informing about the occurrence of the event. ^[22]

Integration Services

Main article: SQL Server Integration Services

SQL Server Integration Services is used to integrate data from different data sources. SQL Server Integration Services ( SSIS) is a component of Microsoft SQL Server 2005 and 2008 It is used for the ETL capabilities for SQL Server for data warehousing needs. Extract Transform and Load ( ETL) is a process in data warehousing that involves extracting data from outside sources A data warehouse is a Repository of an organization's electronically stored data Integration Services includes GUI tools to build data extraction workflows integration various functionality such as extracting data from various sources, querying data, transforming data including aggregating, duplication and merging data, and then loading the transformed data onto other sources, or sending e-mails detailing the status of the operation. A workflow is a depiction of a sequence of operations declared as work of a person work of a simple or complex mechanism work of a group of persons work of an organization of staff Electronic mail, often abbreviated to e-mail, email, or originally eMail, is a Store-and-forward method of writing sending receiving ^[23]

Full Text Search Service

Main article: SQL Server Full Text Search

The SQL Server Full Text Search service architecture

SQL Server Full Text Search service is a specialized indexing and querying service for unstructured text stored in SQL Server databases. SQL Server Full Text Search is an inexact String matching technology for SQL Server. The full text search index can be created on any column with character based text data. It allows for words to be searched for in the text columns. While it can be performed with the SQL LIKE operator, using SQL Server Full Text Search service can be more efficient. Full Text Search (FTS) allows for inexact matching of the source string, indicated by a Rank value which can range from 0 to 1000 - a higher rank means a more accurate match. It also allows linguistic matching ("inflectional search"), i. e. , linguistic variants of a word (such as a verb in a different tense) will also be a match for a given word (but with a lower rank than an exact match). Proximity searches are also supported, i. e. , if the words searched for do not occur in the sequence they are specified in the query but are near each other, they are also considered a match. T-SQL exposes special operators that can be used to access the FTS capabilities. ^[24][25]

The Full Text Search engine is divided into two processes - the Filter Daemon process (msftefd. exe) and the Search process (msftesql. exe). These processes interact with the SQL Server. The Search process includes the indexer (that creates the full text indexes) and the full text query processor. The indexer scans through text columns in the database. It can also index through binary columns, and use iFilters to extract meaningful text from the binary blob (for example, when a Microsoft Word document is stored as an unstructured binary file in a database). IFilters are Plugins that allow the Windows Indexing Service and the newer Windows Desktop Search to index different various File formats so that Microsoft Word is Microsoft 's flagship word processing software. The iFilters are hosted by the Filter Daemon process. Once the text is extracted, the Filter Daemon process breaks it up into a sequence of words and hands it over to the indexer. The indexer filters out noise words, i. e. , words like A, And etc, which occur frequently and are not useful for search. With the remaining words, an inverted index is created, associating each word with the columns they were found in. In Information technology, an inverted index (also referred to as postings file or inverted file) is an index data structure storing a mapping SQL Server itself includes a Gatherer component that monitors changes to tables and invokes the indexer in case of updates. ^[26]

When a full text query is received by the SQL Server query processor, it is handed over to the FTS query processor in the Search process. The FTS query processor breaks up the query into the constituent words, filters out the noise words, and uses an inbuilt thesaurus to find out the linguistic variants for each word. A thesaurus is a book that contains Synonyms and sometimes Antonyms, in contrast to a Dictionary, which contains Definitions and Pronunciations The words are then queried against the inverted index and a rank of their accurateness is computed. The results are returned to the client via the SQL Server process. ^[26]

History

Genesis

The code base for MS SQL Server (prior to version 7. In Computer science, source code (commonly just source or code) is any sequence of statements or declarations written in some Human-readable 0) originated in Sybase SQL Server, and was Microsoft's entry to the enterprise-level database market, competing against Oracle, IBM, and, later, Sybase itself. Adaptive Server Enterprise (ASE is Sybase Corporation's flagship enterprise-class Relational database management system product Oracle Database (commonly referred to as Oracle RDBMS or simply Oracle) is a Relational database management system (RDBMS produced and marketed by International Business Machines Corporation abbreviated IBM and nicknamed "Big Blue", is a multinational Computer Technology Sybase Inc ( is an enterprise software and services company exclusively focused on managing and mobilizing information Microsoft, Sybase and Ashton-Tate originally teamed up to create and market the first version named SQL Server 1. Ashton-Tate ( Ashton-Tate Corporation) was a US based Software company best known for developing the popular DBASE Database application 0 for OS/2 (about 1989) which was essentially the same as Sybase SQL Server 3. OS/2 is a computer Operating system, initially created by Microsoft and IBM, then later developed by IBM exclusively 0 on Unix, VMS, etc. Unix (officially trademarked as UNIX, sometimes also written as Unix with Small caps) is a computer Open Virtual Memory System ( OpenVMS) initially known just as Virtual Memory System ( VMS) is the name of a High-end Computer server Microsoft SQL Server 4. 2 was shipped around 1992 (available bundled with Microsoft OS/2 version 1. OS/2 is a computer Operating system, initially created by Microsoft and IBM, then later developed by IBM exclusively 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, Sybase and Microsoft parted ways and pursued their own design and marketing schemes. Windows NT is a family of Operating systems produced by Microsoft, the first version of which was released in July 1993 Microsoft negotiated exclusive rights to all versions of SQL Server written for Microsoft operating systems. Later, Sybase changed the name of its product to Adaptive Server Enterprise to avoid confusion with Microsoft SQL Server. Adaptive Server Enterprise (ASE is Sybase Corporation's flagship enterprise-class Relational database management system product Until 1994 Microsoft's SQL Server carried three Sybase copyright notices as an indication of its origin.

Since parting ways, several revisions have been done independently. SQL Server 7. 0 was the first true GUI based database server and was a rewrite from the legacy Sybase code. It was succeeded by SQL Server 2000, which was the first edition to be launched in a variant for the IA-64 architecture. Itanium is the brand name for 64-bit Intel Microprocessors that implement the Intel Itanium architecture (formerly called IA-64)

In the six years since release of Microsoft's previous SQL Server product (SQL Server 2000), advancements have been made in performance, the client IDE tools, and several complementary systems that are packaged with SQL Server 2005. These include: an ETL tool (SQL Server Integration Services or SSIS), a Reporting Server, an OLAP and data mining server (Analysis Services), and several messaging technologies, specifically Service Broker and Notification Services. Extract Transform and Load ( ETL) is a process in data warehousing that involves extracting data from outside sources SQL Server Integration Services ( SSIS) is a component of Microsoft SQL Server 2005 and 2008 Online Analytical Processing or OLAP (ˈoʊlæp is an approach to quickly provide answers to analytical queries that are multi-dimensional in nature Data mining is the process of Sorting through large amounts of data and picking out relevant information Microsoft Analysis Services is a group of OLAP and Data Mining services provided in Microsoft SQL Server.

SQL Server 2005

SQL Server 2005, released in November 2005, is the successor to SQL Server 2000. It included native support for managing XML data, in addition to relational data. Don't change "Extensible" A relational database is a Database that groups data using common attributes found in the data set 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 Schema, published as a W3C recommendation in May 2001 is one of several XML schema languages. 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. XQuery is a Query language (with some Programming language features that is designed to query collections of XML data Transact-SQL ( T-SQL) is Microsoft 's and Sybase 's proprietary extension to the 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 TDS packets encapsulated within SOAP requests. A Web service (also Web Service) is defined by the W3C as "a software system designed to support interoperable machine-to-machine interaction SOAP (see below for name and origins is a protocol for exchanging XML -based messages over Computer networks normally using When the data is access over web services, results are returned as XML. ^[27]

For relational data, T-SQL has been augmented with error handling features and support for recursive queries. Transact-SQL ( T-SQL) is Microsoft 's and Sybase 's proprietary extension to the SQL. SQL Server 2005 has also been enhanced with new indexing algorithms and better error recovery systems. Data pages are checksummed for better error resiliency, and optimistic concurrency support has been added for better performance. A checksum is a form of Redundancy check, a simple way to protect the integrity of data by detecting errors in data that are sent through space ( Telecommunications 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 is easier. SQL CLR was introduced with SQL Server 2005 to let it integrate with the .NET Framework. ^[28]

SQL Server 2008

The next version of SQL Server is SQL Server 2008,^[29] code-named "Katmai",^[30] slated to launch on February 27, 2008 and release (RTM) in Q3 2008. Events 1560 - The Treaty of Berwick, which would expel the French from Scotland, is signed by England and the Congregation 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common ^[31][32] The most recent CTP was made available on February 19, 2008. SQL Server 2008 aims^[33] to make data management self-tuning, self organizing, and self maintaining with the development of SQL Server Always On technologies, to provide near-zero downtime. In Control theory a self-tuning system is capable of optimizing its own internal running parameters in order to maximize or minimize the fulfillment of an Objective function SQL Server 2008 will also include support for structured and semi-structured data, including digital media formats for pictures, audio, video and other multimedia data. A data structure in Computer science is a way of storing Data in a computer so that it can be used efficiently In current versions, such multimedia data can be stored as BLOBs (binary large objects), but they are generic bitstreams. A binary large object, also known as a blob, is a collection of Binary data stored as a single entity in a Database management system. Intrinsic awareness of multimedia data will allow specialized functions to be performed on them. According to Paul Flessner, senior Vice President, Server Applications, Microsoft Corp., SQL Server 2008 can be a data storage backend for different varieties of data: XML, email, time/calendar, file, document, spatial, etc as well as perform search, query, analysis, sharing, and synchronization across all data types. Microsoft Corporation is an American multinational Computer technology Corporation, which rose to dominate the Home computer ^[30]

Other new data types include specialized date and time types and a Spatial data type for location-dependent data. ^[34] Better support for unstructured and semi-structured data is provided using the FILESTREAM^[35] data type has been added, which can be used to reference any file stored on the file system. ^[36] Structured data and metadata about the file is stored in SQL Server database, whereas the unstructured component is stored in the file system. Such files can be accessed both via Win32 file handling APIs as well as via SQL Server using T-SQL; doing the latter accesses the file data as a binary BLOB. The Windows API, informally WinAPI, is Microsoft's core set of Application programming interfaces (APIs available in the Microsoft Windows Operating Transact-SQL ( T-SQL) is Microsoft 's and Sybase 's proprietary extension to the SQL. A binary large object, also known as a blob, is a collection of Binary data stored as a single entity in a Database management system. Backing up and restoring the database backs up or restores the referenced files as well. ^[37] SQL Server 2008 also natively supports hierarchical data, and included T-SQL constructs to directly deal with them, without using recursive queries. Transact-SQL ( T-SQL) is Microsoft 's and Sybase 's proprietary extension to the SQL. ^[37]

Spatial data will be stored in two types. A "Flat Earth" (GEOMETRY or planar) data type represents geospatial data which has been projected from its native, spherical, coordinate system into a plane A "Round Earth" data type (GEOGRAPHY) uses an ellipsoidal model in which the Earth is defined as a single continuous entity which does not suffer from the singularities such as the international dateline, poles, or map projection zone "edges". Approximately 70 methods will be available when SQL Server "Katmai" ships to represent spatial operations for the Open Geospatial Consortium Simple Features for SQL, Version 1. The Open Geospatial Consortium ( OGC) is an international voluntary consensus Standards organization. 1^[38].

SQL Server includes better compression features, which also helps in improving scalability. It also includes Resource Governor that allows reserving resources for certain users or workflows. It will also include capabilities for transparent encryption of data as well as compression of backups. ^[35] SQL Server Katmai will support the ADO.NET Entity Framework and the reporting tools, replication, and data definition will be build around the Entity Data Model. ADONET Entity Framework is an Object-relational mapping (ORM framework for the. ADONET Entity Framework is an Object-relational mapping (ORM framework for the. ^[39] SQL Server Reporting Services will gain charting capabilities from the integration of the data visualization products from Dundas Data Visualization Inc. SQL Server Reporting Services (SSRS is a server-based report generation software system from Microsoft. , which was acquired by Microsoft. ^[40] On the management side, SQL Server 2008 will include the Declarative Management Framework which allows configuring policies and constraints, on the entire database or certain tables, declaratively. ^[34] The version of SQL Server Management Studio included with SQL Server 2008 supports IntelliSense for SQL queries. SQL Server Management Studio is a tool included with Microsoft SQL Server 2005 and later versions for configuring managing and administering all components IntelliSense is Microsoft 's implementation of Autocompletion, best known for its use in the Microsoft Visual Studio Integrated development However, with the current CTP, it is limited to SELECT queries; it will be expanded to other T-SQL constructs over later releases. Transact-SQL ( T-SQL) is Microsoft 's and Sybase 's proprietary extension to the SQL. ^[37] SQL Server 2008 will also make the databases available via Windows PowerShell providers and management functionality available as Cmdlets, so that the server and all the running instances can be managed from Windows PowerShell. Windows PowerShell is an extensible command-line shell and associated Scripting language from Microsoft Windows PowerShell is an extensible command-line shell and associated Scripting language from Microsoft ^[41]

Editions

Microsoft makes SQL Server available in multiple versions, with different feature sets and targeting different users. These versions are:^[42][1]

SQL Server Compact Edition (SQL CE)

The compact edition is an embedded database engine. Microsoft SQL Server Compact ( SQL CE) is a compact Relational database produced by Microsoft for applications that run on mobile devices and desktops Due to its small size (2MB DLL footprint), it has a slightly reduced feature set compared to the other editions. It is limited to 4GB maximum database size and cannot be run as a Windows service, Compact Edition must be hosted by the application using it.

SQL Server Express Edition

SQL Server Express Edition is a scaled down, free edition of SQL Server, which includes the core database engine. Microsoft SQL Server Express is the freely-downloadable and distributable version of Microsoft 's SQL Server Relational database management system. While there are no limitations on the number of databases or users supported, it is limited to using one processor, 1 GB memory and 4 GB database files. The entire database is stored in a single . mdf file, and thus making it suitable for XCOPY deployment. In Computing, Xcopy is command used for copying multiple files or entire directory trees from one directory to another and for copying files It is intended as a replacement for MSDE. MSDE stands for MS Data Engine, Microsoft Desktop Engine or Microsoft SQL Server Desktop Engine. The Full-Text Search Service is made available as a free add-on to SQL Server Express edition as well. In addition, a stripped down version of SQL Server Management Studio is also available for this edition.

SQL Server Workgroup Edition

SQL Server Workgroup Edition includes the core database functionality but does not include the additional services.

SQL Server Standard Edition

SQL Server Standard edition includes the core database engine, along with the stand-alone services. It differs from Enterprise edition in that it supports less number of active instances (number of nodes in a cluster) and does not include some high-availability functions such as hot-add memory (allowing memory to be added while the server is still running), and parallel indexes.

SQL Server Enterprise Edition

SQL Server Enterprise Edition is the full-featured version of SQL Server, including both the core database engine and add-on services, while including a range of tools for creating and managing an SQL Server cluster.

SQL Server Developer Edition

SQL Server Developer Edition includes the same features as SQL Server Enterprise Edition, but is limited by the license to be only used as a development and test system, and not as production server. This version is available to download by students free of charge as a part of Microsoft's DreamSpark program. Microsoft Corporation is an American multinational Computer technology Corporation, which rose to dominate the Home computer DreamSpark is a program set up by Microsoft to provide students with software design and development tools at no charge

Tools

SQLCMD

SQLCMD is a command line application that comes with Microsoft SQL Server, and exposes the management features of SQL Server. It allows SQL queries to be written and executed from the command prompt. It can also act as a scripting language to create and run a set of SQL statements as a script. "Scripting" redirects here For other uses see Script. Such scripts are stored as a . sql file, and are used either for management of databases or to create the database schema during the deployment of a database.

Visual Studio

Microsoft Visual Studio includes native support for data programming with Microsoft SQL Server. Microsoft Visual Studio is the main Integrated Development Environment (IDE from Microsoft. It can be used to write and debug code to be executed by SQL CLR. It also includes a data designer that can be used to graphically create, view or edit database schemas. Queries can be created either visually or using code. SSMS 2008 onwards, provides intellisense for SQL queries as well. IntelliSense is Microsoft 's implementation of Autocompletion, best known for its use in the Microsoft Visual Studio Integrated development

SQL Server Management Studio

Microsoft SQL Server Management Studio showing a query, the results of the query, and the Object Explorer pane while connected to a SQL Server database engine instance.

SQL Server Management Studio is a GUI tool included with SQL Server 2005 and later for configuring, managing, and administering all components within Microsoft SQL Server. SQL Server Management Studio is a tool included with Microsoft SQL Server 2005 and later versions for configuring managing and administering all components The tool includes both script editors and graphical tools which work with objects and features of the server. ^[43] SQL Server Management Studio replaces Enterprise Manager as the primary management interface for Microsoft SQL Server since SQL Server 2005. Enterprise Manager is the primary administrative tool for Microsoft SQL Server 2000 and provides a MMC –based user interface that allows users to Define A version of SQL Server Management Studio is also available for SQL Server Express Edition, for which it is known as SQL Server Management Studio Express (SSMSE). ^[44]

A central feature of SQL Server Management Studio is the Object Explorer, which allows the user to browse, select, and act upon any of the objects within the server. ^[45] It can be used to visually observe and analyze query plans and optimize the database performance, among others. ^[46] SQL Server Management Studio can also be used to create a new database, alter any existing database schema by adding or modifying tables and indexes or analyze performance. It includes the query windows which provides a GUI based interface to write and execute queries. ^[1]

Business Intelligence Development Studio

Business Intelligence Development Studio (BIDS) is the IDE from Microsoft used for developing data analysis and Business Intelligence solutions utilizing the Microsoft SQL Server Analysis Services, Reporting Services and Integration Services. Business Intelligence Development Studio ( BIDS) is the IDE from Microsoft used for developing data analysis and Business Intelligence solutions In Computing, an integrated development environment ( IDE) is a Software application that provides comprehensive facilities to Computer programmers Microsoft Corporation is an American multinational Computer technology Corporation, which rose to dominate the Home computer Business intelligence ( BI) refers to technologies applications and practices for the collection integration analysis and presentation of business Information and Microsoft Analysis Services is a group of OLAP and Data Mining services provided in Microsoft SQL Server. SQL Server Reporting Services (SSRS is a server-based report generation software system from Microsoft. SQL Server Integration Services ( SSIS) is a component of Microsoft SQL Server 2005 and 2008 It is based on the Microsoft Visual Studio development environment but customizes with the SQL Server services-specific extensions and project types, including tools, controls and projects for reports (using Reporting Services), Cubes and data mining structures (using Analysis Services). Microsoft Visual Studio is the main Integrated Development Environment (IDE from Microsoft. An OLAP cube is a data structure that allows fast analysis of data Data mining is the process of Sorting through large amounts of data and picking out relevant information ^[47]

Programmability

T-SQL

Main article: T-SQL

T-SQL (Transact-SQL) is the primary means of programming and managing SQL Server. Transact-SQL ( T-SQL) is Microsoft 's and Sybase 's proprietary extension to the SQL. It exposes keywords for the operations that can be performed on SQL Server, including creating and altering database schemas, entering and editing data in the database as well as monitoring and managing the server itself. Client applications, both which consume data or manage the server, leverage SQL Server functionality by sending T-SQL queries and statements which are then processed by the server and results (or errors) returned to the client application. SQL Server allows it to be managed using T-SQL. For this it exposes read only tables from which server statistics can be read. Management functionality is exposed via system-defined stored procedures which can be invoked from T-SQL queries to perform the management operation. ^[48]

SQL Native Client

SQL Native Client is the native client side data access library for Microsoft SQL Server, version 2005 onwards. In Computer science, a library is a collection of Subroutines used to develop Software. It natively implements support for the SQL Server features including the TDS implementation, support for mirrored SQL Server databases, full support for all data types supported by SQL Server, asynchronous operations, query notifications, encryption support, as well as receiving multiple result sets in a single database session. SQL Native Client is used under the hood by SQL Server plug-ins for other data access technologies, including ADO or OLE DB. Microsoft's ActiveX Data Objects ( ADO) is a set of Component Object Model (COM objects for accessing data sources OLE DB ( Object Linking and Embedding Database, sometimes written as OLEDB or OLE-DB) is an API designed by Microsoft for accessing It is also used by the native SQL Server ADO.NET provider, SqlClient. ADONET is a set of computer software components that can be used by programmers to access data and data services The SQL Native Client can also be directly used, bypassing the generic data access layers. ^[49]

References

See also

• SQL Server Data Services

External links

• SQL Server Official Site
• Longer version of the history from a dev team member
• Factsheet for SQL Server developers
• Blog and Forum for SQL Server administrators and developers

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