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138-477: Microsoft SQL Server (Structured Query Language) is a proprietary relational database management system developed by Microsoft . As a database server , it is a software product with the primary function of storing and retrieving data as requested by other software applications —which may run either on the same computer or on another computer across a network (including the Internet). Microsoft markets at least

276-408: A .ndf extension, are used to allow the data of a single database to be spread across more than one file, and optionally across more than one file system. Log files are identified with the .ldf extension. 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

414-405: A .sql file, and are used either for management of databases or to create the database schema during the deployment of a database. SQLCMD was introduced with SQL Server 2005 and has continued through SQL Server versions 2008, 2008 R2, 2012, 2014, 2016 and 2019. Its predecessor for earlier versions was OSQL and ISQL, which were functionally equivalent as it pertains to T-SQL execution, and many of

552-457: 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. The page type defines the data contained in the page. This data includes: data stored in the database, an index, an allocation map, which holds information about how pages are allocated to tables and indexes; and a change map which holds information about

690-400: A challenge. In a heterogeneous CPU-GPU cluster with a complex application environment, the performance of each job depends on the characteristics of the underlying cluster. Therefore, mapping tasks onto CPU cores and GPU devices provides significant challenges. This is an area of ongoing research; algorithms that combine and extend MapReduce and Hadoop have been proposed and studied. When

828-643: A cluster requires parallel language primitives and suitable tools such as those discussed by the High Performance Debugging Forum (HPDF) which resulted in the HPD specifications. Tools such as TotalView were then developed to debug parallel implementations on computer clusters which use Message Passing Interface (MPI) or Parallel Virtual Machine (PVM) for message passing. The University of California, Berkeley Network of Workstations (NOW) system gathers cluster data and stores them in

966-570: A cluster was the Burroughs B5700 in the mid-1960s. This allowed up to four computers, each with either one or two processors, to be tightly coupled to a common disk storage subsystem in order to distribute the workload. Unlike standard multiprocessor systems, each computer could be restarted without disrupting overall operation. The first commercial loosely coupled clustering product was Datapoint Corporation's "Attached Resource Computer" (ARC) system, developed in 1977, and using ARCnet as

1104-408: A database can also contain other objects including views , stored procedures , indexes and constraints , along with a transaction log. A SQL Server database can contain a maximum of 2 objects, and can span multiple OS-level files with a maximum file size of 2 bytes (1 exabyte). The data in the database are stored in primary data files with an extension .mdf . Secondary data files, identified with

1242-671: A database does not implement all of Codd's rules (or the current understanding on the relational model, as expressed by Christopher J. Date , Hugh Darwen and others), it is not relational. This view, shared by many theorists and other strict adherents to Codd's principles, would disqualify most DBMSs as not relational. For clarification, they often refer to some RDBMSs as truly-relational database management systems (TRDBMS), naming others pseudo-relational database management systems (PRDBMS). As of 2009, most commercial relational DBMSs employ SQL as their query language . Alternative query languages have been proposed and implemented, notably

1380-488: A database, while a system such as PARMON, developed in India, allows visually observing and managing large clusters. Application checkpointing can be used to restore a given state of the system when a node fails during a long multi-node computation. This is essential in large clusters, given that as the number of nodes increases, so does the likelihood of node failure under heavy computational loads. Checkpointing can restore

1518-409: A dedicated network, is densely located, and probably has homogeneous nodes. The other extreme is where a computer job uses one or few nodes, and needs little or no inter-node communication, approaching grid computing . In a Beowulf cluster , the application programs never see the computational nodes (also called slave computers) but only interact with the "Master" which is a specific computer handling

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1656-467: A dozen different editions of Microsoft SQL Server, aimed at different audiences and for workloads ranging from small single-machine applications to large Internet-facing applications with many concurrent users . The history of Microsoft SQL Server begins with the first Microsoft SQL Server product—SQL Server 1.0, a 16-bit server for the OS/2 operating system in 1989—and extends to the current day. Its name

1794-717: A file in the filesystem. Notification Services was discontinued by Microsoft with the release of SQL Server 2008 in August 2008, and is no longer an officially supported component of the SQL Server database platform. SQL Server Integration Services (SSIS) provides ETL capabilities for SQL Server for data import , data integration and data warehousing needs. Integration Services includes GUI tools to build workflows such as extracting data from various sources, querying data, transforming data—including aggregation, de-duplication, de-/normalization and merging of data—and then exporting

1932-609: A handful of nodes to some of the fastest supercomputers in the world such as IBM's Sequoia . Prior to the advent of clusters, single-unit fault tolerant mainframes with modular redundancy were employed; but the lower upfront cost of clusters, and increased speed of network fabric has favoured the adoption of clusters. In contrast to high-reliability mainframes, clusters are cheaper to scale out, but also have increased complexity in error handling, as in clusters error modes are not opaque to running programs. The desire to get more computing power and better reliability by orchestrating

2070-504: A high-availability approach, etc. " Load-balancing " clusters are configurations in which cluster-nodes share computational workload to provide better overall performance. For example, a web server cluster may assign different queries to different nodes, so the overall response time will be optimized. However, approaches to load-balancing may significantly differ among applications, e.g. a high-performance cluster used for scientific computations would balance load with different algorithms from

2208-685: A large and shared file server that stores global persistent data, accessed by the slaves as needed. A special purpose 144-node DEGIMA cluster is tuned to running astrophysical N-body simulations using the Multiple-Walk parallel tree code, rather than general purpose scientific computations. Due to the increasing computing power of each generation of game consoles , a novel use has emerged where they are repurposed into High-performance computing (HPC) clusters. Some examples of game console clusters are Sony PlayStation clusters and Microsoft Xbox clusters. Another example of consumer game product

2346-402: A large number of computers clustered together, this lends itself to the use of distributed file systems and RAID , both of which can increase the reliability and speed of a cluster. One of the issues in designing a cluster is how tightly coupled the individual nodes may be. For instance, a single computer job may require frequent communication among nodes: this implies that the cluster shares

2484-506: A new database, alter any existing database schema by adding or modifying tables and indexes, or analyze performance. It includes the query windows which provide a GUI based interface to write and execute queries. Azure Data Studio is a cross platform query editor available as an optional download. The tool allows users to write queries; export query results; commit SQL scripts to Git repositories and perform basic server diagnostics. Azure Data Studio supports Windows, Mac and Linux systems. It

2622-399: A new row is written to the table, a new unique value for the primary key is generated; this is the key that the system uses primarily for accessing the table. System performance is optimized for PKs. Other, more natural keys may also be identified and defined as alternate keys (AK). Often several columns are needed to form an AK (this is one reason why a single integer column is usually made

2760-455: A node in a cluster fails, strategies such as " fencing " may be employed to keep the rest of the system operational. Fencing is the process of isolating a node or protecting shared resources when a node appears to be malfunctioning. There are two classes of fencing methods; one disables a node itself, and the other disallows access to resources such as shared disks. The STONITH method stands for "Shoot The Other Node In The Head", meaning that

2898-428: A number of low-cost commercial off-the-shelf computers has given rise to a variety of architectures and configurations. The computer clustering approach usually (but not always) connects a number of readily available computing nodes (e.g. personal computers used as servers) via a fast local area network . The activities of the computing nodes are orchestrated by "clustering middleware", a software layer that sits atop

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3036-459: A part of the database engine, provides a reliable messaging and message queuing platform for SQL Server applications. Service broker services consists of the following parts: The message type defines the data format used for the message. This can be an XML object, plain text or binary data, as well as a null message body for notifications. The contract defines which messages are used in an conversation between services and who can put messages in

3174-400: A query, then the query optimizer looks at the database schema , the database statistics and the system load at that time. 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

3312-434: A rank of their accurateness is computed. The results are returned to the client via the SQL Server process. 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. Such scripts are stored as

3450-471: A remote SQL server and push the script executions to it, or they can run a R or Python scripts as an external script inside a T-SQL query. The trained machine learning model can be stored inside a database and used for scoring. Used inside an instance, programming environment. For cross-instance applications, Service Broker communicates over TCP/IP and allows the different components to be synchronized, via exchange of messages. The Service Broker, which runs as

3588-427: A run-time environment for message-passing, task and resource management, and fault notification. PVM can be used by user programs written in C, C++, or Fortran, etc. MPI emerged in the early 1990s out of discussions among 40 organizations. The initial effort was supported by ARPA and National Science Foundation . Rather than starting anew, the design of MPI drew on various features available in commercial systems of

3726-440: A simple two-node system which just connects two personal computers, or may be a very fast supercomputer . A basic approach to building a cluster is that of a Beowulf cluster which may be built with a few personal computers to produce a cost-effective alternative to traditional high-performance computing . An early project that showed the viability of the concept was the 133-node Stone Soupercomputer . The developers used Linux ,

3864-451: A single computer, while typically being much more cost-effective than single computers of comparable speed or availability. Computer clusters emerged as a result of the convergence of a number of computing trends including the availability of low-cost microprocessors, high-speed networks, and software for high-performance distributed computing . They have a wide range of applicability and deployment, ranging from small business clusters with

4002-645: A single database session. SQL Server Native Client is used under the hood by SQL Server plug-ins for other data access technologies, including ADO or OLE DB . The SQL Server Native Client can also be directly used, bypassing the generic data access layers. On November 28, 2011, a preview release of the SQL Server ODBC driver for Linux was released. Microsoft SQL Server 2005 includes a component named SQL CLR ("Common Language Runtime") via which it integrates with .NET Framework . Unlike most other applications that use .NET Framework, SQL Server itself hosts

4140-455: A single relation, even though they may grab information from several relations. Also, derived relations can be used as an abstraction layer . A domain describes the set of possible values for a given attribute, and can be considered a constraint on the value of the attribute. Mathematically, attaching a domain to an attribute means that any value for the attribute must be an element of the specified set. The character string "ABC" , for instance,

4278-467: A small number of users need to take advantage of the parallel processing capabilities of the cluster and partition "the same computation" among several nodes. Automatic parallelization of programs remains a technical challenge, but parallel programming models can be used to effectuate a higher degree of parallelism via the simultaneous execution of separate portions of a program on different processors. Developing and debugging parallel programs on

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4416-558: A system. For increased security, the system design may grant access to only the stored procedures and not directly to the tables. Fundamental stored procedures contain the logic needed to insert new and update existing data. More complex procedures may be written to implement additional rules and logic related to processing or selecting the data. The relational database was first defined in June 1970 by Edgar Codd , of IBM's San Jose Research Laboratory . Codd's view of what qualifies as an RDBMS

4554-414: A tuple (restricting combinations of attributes) or to an entire relation. Since every attribute has an associated domain, there are constraints ( domain constraints ). The two principal rules for the relational model are known as entity integrity and referential integrity . Every relation /table has a primary key, this being a consequence of a relation being a set . A primary key uniquely specifies

4692-476: A tuple within a table. While natural attributes (attributes used to describe the data being entered) are sometimes good primary keys, surrogate keys are often used instead. A surrogate key is an artificial attribute assigned to an object which uniquely identifies it (for instance, in a table of information about students at a school they might all be assigned a student ID in order to differentiate them). The surrogate key has no intrinsic (inherent) meaning, but rather

4830-565: A web-server cluster which may just use a simple round-robin method by assigning each new request to a different node. Computer clusters are used for computation-intensive purposes, rather than handling IO-oriented operations such as web service or databases. For instance, a computer cluster might support computational simulations of vehicle crashes or weather. Very tightly coupled computer clusters are designed for work that may approach " supercomputing ". " High-availability clusters " (also known as failover clusters, or HA clusters) improve

4968-409: Is 16.0.1000.6. Microsoft makes SQL Server available in multiple editions, with different feature sets and targeting different users. These editions are: Tools published by Microsoft include: The 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). TDS

5106-510: Is a GUI tool included with SQL Server 2005 and later for configuring, managing, and administering all components within Microsoft SQL Server. The tool includes both script editors and graphical tools that work with objects and features of the server. SQL Server Management Studio replaces Enterprise Manager as the primary management interface for Microsoft SQL Server since SQL Server 2005. A version of SQL Server Management Studio

5244-433: Is a mechanism for generating data-driven notifications, which are sent to Notification Services subscribers. 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 can use one of three methods to send a message to the subscriber informing about the occurrence of the event. These methods include SMTP, SOAP, or by writing to

5382-454: Is a report generation environment for data gathered from SQL Server databases. It is administered via a web interface. Reporting services features a web services interface to support the development of custom reporting applications. Reports are created as RDL files. Reports can be designed using recent versions of Microsoft Visual Studio (Visual Studio.NET 2003, 2005, and 2008) with Business Intelligence Development Studio , installed or with

5520-523: Is also available for SQL Server Express Edition, for which it is known as SQL Server Management Studio Express (SSMSE). 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. It can be used to visually observe and analyze query plans and optimize the database performance, among others. SQL Server Management Studio can also be used to create

5658-424: 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, TDS packets can be encased in other physical transport dependent protocols, including TCP/IP , named pipes , and shared memory . Consequently, access to SQL Server

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5796-503: Is analogous to using the index of a book to go directly to the page on which the information you are looking for is found, so that you do not have to read the entire book to find what you are looking for. Relational databases typically supply multiple indexing techniques, each of which is optimal for some combination of data distribution, relation size, and typical access pattern. Indices are usually implemented via B+ trees , R-trees , and bitmaps . Indices are usually not considered part of

5934-932: Is available over these protocols. In addition, the SQL Server API is also exposed over web services . Data storage is a database , which is a collection of tables with typed columns. SQL Server supports different data types, including primitive 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. The rounding of floats to integers uses either Symmetric Arithmetic Rounding or Symmetric Round Down ( fix ) depending on arguments: SELECT Round(2.5, 0) gives 3. Microsoft SQL Server also allows user-defined composite types (UDTs) to be defined and used. It also makes server statistics available as virtual tables and views (called Dynamic Management Views or DMVs). In addition to tables,

6072-541: Is based on the Microsoft Visual Studio development environment but is customized 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). For SQL Server 2012 and later, this IDE has been renamed SQL Server Data Tools (SSDT). Relational database management system The concept of relational database

6210-588: 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. 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 meantime. 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

6348-497: Is entirely descriptive, it being server software that responds to queries in the SQL language. As of February 2024, the following versions are supported by Microsoft: From SQL Server 2016 onward, the product is supported on x64 processors only and must have 1.4 GHz processor as a minimum, 2.0 GHz or faster is recommended. The current version is Microsoft SQL Server 2022, released November 16, 2022. The RTM version

6486-435: 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. SQL Server also allows stored procedures to be defined. 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

6624-399: 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 possibly a sequence of pages, called an allocation unit ) and replaced with a pointer to the data. For physical storage of a table, its rows are divided into a series of partitions (numbered 1 to n). The partition size

6762-591: 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

6900-497: Is not in the integer domain, but the integer value 123 is. Another example of domain describes the possible values for the field "CoinFace" as ("Heads","Tails"). So, the field "CoinFace" will not accept input values like (0,1) or (H,T). Constraints are often used to make it possible to further restrict the domain of an attribute. For instance, a constraint can restrict a given integer attribute to values between 1 and 10. Constraints provide one method of implementing business rules in

7038-410: 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. 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

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7176-453: Is summarized in Codd's 12 rules . A relational database has become the predominant type of database. Other models besides the relational model include the hierarchical database model and the network model . The table below summarizes some of the most important relational database terms and the corresponding SQL term: In a relational database, a relation is a set of tuples that have

7314-657: Is the Nvidia Tesla Personal Supercomputer workstation, which uses multiple graphics accelerator processor chips. Besides game consoles, high-end graphics cards too can be used instead. The use of graphics cards (or rather their GPU's) to do calculations for grid computing is vastly more economical than using CPU's, despite being less precise. However, when using double-precision values, they become as precise to work with as CPU's and are still much less costly (purchase cost). Computer clusters have historically run on separate physical computers with

7452-489: Is the native client side data access library for Microsoft SQL Server, version 2005 onwards. It natively implements support for the SQL Server features including the Tabular Data Stream 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

7590-446: Is useful through its ability to uniquely identify a tuple. Another common occurrence, especially in regard to N:M cardinality is the composite key . A composite key is a key made up of two or more attributes within a table that (together) uniquely identify a record. Foreign key refers to a field in a relational table that matches the primary key column of another table. It relates the two keys. Foreign keys need not have unique values in

7728-405: 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 computer cluster . Rows in each partition are stored in either B-tree or heap structure. If the table has an associated, clustered index to allow fast retrieval of rows, the rows are stored in-order according to their index values, with a B-tree providing

7866-804: The Tandem NonStop (a 1976 high-availability commercial product) and the IBM S/390 Parallel Sysplex (circa 1994, primarily for business use). Within the same time frame, while computer clusters used parallelism outside the computer on a commodity network, supercomputers began to use them within the same computer. Following the success of the CDC 6600 in 1964, the Cray 1 was delivered in 1976, and introduced internal parallelism via vector processing . While early supercomputers excluded clusters and relied on shared memory , in time some of

8004-590: The ADO.NET APIs like any other managed application that accesses SQL Server data. 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. Such connections are called context connections and are set by setting context connection parameter to true in

8142-510: The Linux operating system. Clusters are primarily designed with performance in mind, but installations are based on many other factors. Fault tolerance ( the ability of a system to continue operating despite a malfunctioning node ) enables scalability , and in high-performance situations, allows for a low frequency of maintenance routines, resource consolidation (e.g., RAID ), and centralized management. Advantages include enabling data recovery in

8280-598: The Oracle Cluster File System . Two widely used approaches for communication between cluster nodes are MPI ( Message Passing Interface ) and PVM ( Parallel Virtual Machine ). PVM was developed at the Oak Ridge National Laboratory around 1989 before MPI was available. PVM must be directly installed on every cluster node and provides a set of software libraries that paint the node as a "parallel virtual machine". PVM provides

8418-587: The Parallel Virtual Machine toolkit and the Message Passing Interface library to achieve high performance at a relatively low cost. Although a cluster may consist of just a few personal computers connected by a simple network, the cluster architecture may also be used to achieve very high levels of performance. The TOP500 organization's semiannual list of the 500 fastest supercomputers often includes many clusters, e.g.

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8556-597: The XML for Analysis standard as the underlying communication protocol. The cube data can be accessed using MDX and LINQ queries. Data mining specific functionality is exposed via the DMX query language. 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. SQL Server Reporting Services (SSRS)

8694-481: The kernel that provide for automatic process migration among homogeneous nodes. OpenSSI , openMosix and Kerrighed are single-system image implementations. Microsoft Windows computer cluster Server 2003 based on the Windows Server platform provides pieces for high-performance computing like the job scheduler, MSMPI library and management tools. gLite is a set of middleware technologies created by

8832-417: The normal forms . Connolly and Begg define database management system (DBMS) as a "software system that enables users to define, create, maintain and control access to the database". RDBMS is an extension of that initialism that is sometimes used when the underlying database is relational. An alternative definition for a relational database management system is a database management system (DBMS) based on

8970-569: The relational model . Most databases in widespread use today are based on this model. RDBMSs have been a common option for the storage of information in databases used for financial records, manufacturing and logistical information, personnel data, and other applications since the 1980s. Relational databases have often replaced legacy hierarchical databases and network databases , because RDBMS were easier to implement and administer. Nonetheless, relational stored data received continued, unsuccessful challenges by object database management systems in

9108-493: The .NET Framework runtime , i.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 . Managed code can also be used to define UDT's ( user defined types ), which can persist in

9246-496: The 1980s and 1990s, (which were introduced in an attempt to address the so-called object–relational impedance mismatch between relational databases and object-oriented application programs), as well as by XML database management systems in the 1990s. However, due to the expanse of technologies, such as horizontal scaling of computer clusters , NoSQL databases have recently become popular as an alternative to RDBMS databases. Distributed Relational Database Architecture (DRDA)

9384-561: The 1980s, so were supercomputers . One of the elements that distinguished the three classes at that time was that the early supercomputers relied on shared memory . Clusters do not typically use physically shared memory, while many supercomputer architectures have also abandoned it. However, the use of a clustered file system is essential in modern computer clusters. Examples include the IBM General Parallel File System , Microsoft's Cluster Shared Volumes or

9522-451: The GNBD server. Load balancing clusters such as web servers use cluster architectures to support a large number of users and typically each user request is routed to a specific node, achieving task parallelism without multi-node cooperation, given that the main goal of the system is providing rapid user access to shared data. However, "computer clusters" which perform complex computations for

9660-448: The PK). Both PKs and AKs have the ability to uniquely identify a row within a table. Additional technology may be applied to ensure a unique ID across the world, a globally unique identifier , when there are broader system requirements. The primary keys within a database are used to define the relationships among the tables. When a PK migrates to another table, it becomes a foreign key (FK) in

9798-550: The SQL server instance, allowing people to do machine learning and data analytics without having to send data across the network or be limited by the memory of their own computers. The services come with Microsoft's R and Python distributions that contain commonly used packages for data science, along with some proprietary packages (e.g. revoscalepy , RevoScaleR , microsoftml) that can be used to create machine models at scale. Analysts can either configure their client machine to connect to

9936-438: The availability of the cluster approach. They operate by having redundant nodes , which are then used to provide service when system components fail. HA cluster implementations attempt to use redundancy of cluster components to eliminate single points of failure . There are commercial implementations of High-Availability clusters for many operating systems. The Linux-HA project is one commonly used free software HA package for

10074-438: The basis of interaction among these tables. These relationships can be modelled as an entity-relationship model . In order for a database management system (DBMS) to operate efficiently and accurately, it must use ACID transactions . Part of the programming within a RDBMS is accomplished using stored procedures (SPs). Often procedures can be used to greatly reduce the amount of information transferred within and outside of

10212-488: The challenges in the use of a computer cluster is the cost of administrating it which can at times be as high as the cost of administrating N independent machines, if the cluster has N nodes. In some cases this provides an advantage to shared memory architectures with lower administration costs. This has also made virtual machines popular, due to the ease of administration. When a large multi-user cluster needs to access very large amounts of data, task scheduling becomes

10350-443: The changes made to other pages since last backup or logging, or contain large data types such as image or text. While a 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

10488-426: The client application. 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. It is also possible to create linked Servers using T-SQL. Linked servers allow a single query to process operations performed on multiple servers. SQL Server Native Client

10626-420: The client as input parameters, and send back results as output parameters. They can call defined functions, and other stored procedures, including the same stored procedure (up to a set number of times). They can be selectively provided access to . 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

10764-563: The client every time (as it can be accessed by name), it reduces network traffic and somewhat improves performance. Execution plans for stored procedures are also cached as necessary. T-SQL (Transact-SQL) is Microsoft's proprietary procedural language extension for SQL Server. It provides REPL (Read-Eval-Print-Loop) instructions that extend standard SQL's instruction set for Data Manipulation ( DML ) and Data Definition ( DDL ) instructions, including SQL Server-specific settings, security and database statistics management. It exposes keywords for

10902-522: The cluster interface. Clustering per se did not really take off until Digital Equipment Corporation released their VAXcluster product in 1984 for the VMS operating system. The ARC and VAXcluster products not only supported parallel computing , but also shared file systems and peripheral devices. The idea was to provide the advantages of parallel processing, while maintaining data reliability and uniqueness. Two other noteworthy early commercial clusters were

11040-409: The cluster. This property of computer clusters can allow for larger computational loads to be executed by a larger number of lower performing computers. When adding a new node to a cluster, reliability increases because the entire cluster does not need to be taken down. A single node can be taken down for maintenance, while the rest of the cluster takes on the load of that individual node. If you have

11178-402: The columns represent values attributed to that instance (such as address or price). For example, each row of a class table corresponds to a class, and a class corresponds to multiple students, so the relationship between the class table and the student table is "one to many" Each row in a table has its own unique key. Rows in a table can be linked to rows in other tables by adding a column for

11316-510: The command line parameters are identical, although SQLCMD adds extra versatility. Microsoft Visual Studio includes native support for data programming with Microsoft SQL Server. 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. SQL Server Management Studio

11454-532: 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. It also provides access to the XML features in SQL Server, including XQuery support. These enhancements are also available in T-SQL Procedures in consequence of

11592-401: The database and support subsequent data use within the application layer. SQL implements constraint functionality in the form of check constraints . Constraints restrict the data that can be stored in relations . These are usually defined using expressions that result in a Boolean value, indicating whether or not the data satisfies the constraint. Constraints can apply to single attributes, to

11730-469: The database, as they are considered an implementation detail, though indices are usually maintained by the same group that maintains the other parts of the database. The use of efficient indexes on both primary and foreign keys can dramatically improve query performance. This is because B-tree indexes result in query times proportional to log(n) where n is the number of rows in a table and hash indexes result in constant time queries (no size dependency as long as

11868-410: The database, identified by their respective transaction IDs. The main mode of retrieving data from a SQL Server database is querying for it. 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. The query declaratively specifies what is to be retrieved. It is processed by the query processor, which figures out

12006-519: The database. Managed code is compiled to CLI assemblies and after being verified for type safety , registered at the database. After that, they can be invoked like any other procedure. However, only a subset of the Base Class Library is available, when running code under SQL CLR. Most APIs relating to user interface functionality are not available. When writing code for SQL CLR, data stored in SQL Server databases can be accessed using

12144-439: 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

12282-761: 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 yield higher performance. SQL Server also includes two more lightweight mutual exclusion solutions—latches and spinlocks—which are less robust than locks but are less resource intensive. 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 are to kill one of

12420-415: The event of a disaster and providing parallel data processing and high processing capacity. In terms of scalability, clusters provide this in their ability to add nodes horizontally. This means that more computers may be added to the cluster, to improve its performance, redundancy and fault tolerance. This can be an inexpensive solution for a higher performing cluster compared to scaling up a single node in

12558-432: The fastest supercomputers (e.g. the K computer ) relied on cluster architectures. Computer clusters may be configured for different purposes ranging from general purpose business needs such as web-service support, to computation-intensive scientific calculations. In either case, the cluster may use a high-availability approach. Note that the attributes described below are not exclusive and a "computer cluster" may also use

12696-564: The first RDBMS for Macintosh began being developed, code-named Silver Surfer, and was released in 1987 as 4th Dimension and known today as 4D. The first systems that were relatively faithful implementations of the relational model were from: The most common definition of an RDBMS is a product that presents a view of data as a collection of rows and columns, even if it is not based strictly upon relational theory . By this definition, RDBMS products typically implement some but not all of Codd's 12 rules. A second school of thought argues that if

12834-409: The five leading proprietary software relational database vendors by revenue were Oracle (48.8%), IBM (20.2%), Microsoft (17.0%), SAP including Sybase (4.6%), and Teradata (3.7%). Cluster computing A computer cluster is a set of computers that work together so that they can be viewed as a single system. Unlike grid computers , computer clusters have each node set to perform

12972-470: The heap structure has performance advantages over the clustered structure. Both heaps and B-trees can span multiple allocation units. SQL Server buffers pages in RAM to minimize disk 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

13110-435: The included Report Builder . Once created, RDL files can be rendered in a variety of formats, including Excel, PDF , CSV , XML , BMP , EMF , GIF , JPEG , PNG , and TIFF , and HTML Web Archive. Originally introduced as a post-release add-on for SQL Server 2000, Notification Services was bundled as part of the Microsoft SQL Server platform for the first and only time with SQL Server 2005. SQL Server Notification Services

13248-482: The index. 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. A table without a clustered index is stored in an unordered heap structure. However, the table may have non-clustered indices to allow fast retrieval of rows. In some situations

13386-474: 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). The iFilters are hosted by the Filter Daemon process. Once

13524-513: The indexer in case of updates. 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. The words are then queried against the inverted index and

13662-514: The introduction of the new XML Datatype (query, value, nodes functions). SQL Server also includes an assortment of add-on services. While these are not essential for the operation of the database system, they 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. The SQL Server Machine Learning services operates within

13800-400: The join, but result in different execution plans. In such case, SQL Server chooses the plan that is expected to yield the results in the shortest possible time. This is called query optimization and is performed by the query processor itself. 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

13938-492: The network, or database caches on the client side. Replication Services 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: SQL Server Analysis Services (SSAS) adds OLAP and data mining capabilities for SQL Server databases. The OLAP engine supports MOLAP , ROLAP and HOLAP storage modes for data. Analysis Services supports

14076-428: The network. Also, service broker supports security features like network authentication (using NTLM , Kerberos , or authorization certificates ), integrity checking, and message encryption . 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

14214-447: The nodes and allows the users to treat the cluster as by and large one cohesive computing unit, e.g. via a single system image concept. Computer clustering relies on a centralized management approach which makes the nodes available as orchestrated shared servers. It is distinct from other approaches such as peer-to-peer or grid computing which also use many nodes, but with a far more distributed nature . A computer cluster may be

14352-410: 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 that consume data or manage the server will leverage SQL Server functionality by sending T-SQL queries and statements which are then processed by the server and results (or errors) returned to

14490-400: The optimistic concurrency control mechanism, which is similar to the multiversion concurrency control used in other databases. 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

14628-519: The original eight including relational comparison operators and extensions that offer support for nesting and hierarchical data, among others. Normalization was first proposed by Codd as an integral part of the relational model. It encompasses a set of procedures designed to eliminate non-simple domains (non-atomic values) and the redundancy (duplication) of data, which in turn prevents data manipulation anomalies and loss of data integrity. The most common forms of normalization applied to databases are called

14766-506: The other table. When each cell can contain only one value and the PK migrates into a regular entity table, this design pattern can represent either a one-to-one or one-to-many relationship. Most relational database designs resolve many-to-many relationships by creating an additional table that contains the PKs from both of the other entity tables – the relationship becomes an entity;

14904-446: The pre-1996 implementation of Ingres QUEL . A relational model organizes data into one or more tables (or "relations") of columns and rows , with a unique key identifying each row. Rows are also called records or tuples . Columns are also called attributes. Generally, each table/relation represents one "entity type" (such as customer or product). The rows represent instances of that type of entity (such as "Lee" or "chair") and

15042-403: The queue. The queue acts as storage provider for the messages. They are internally implemented as tables by SQL Server, but do not support insert, update, or delete functionality. The service program receives and processes service broker messages. Usually the service program is implemented as stored procedure or CLR application. Routes are network addresses where the service broker is located on

15180-458: The referencing relation. A foreign key can be used to cross-reference tables, and it effectively uses the values of attributes in the referenced relation to restrict the domain of one or more attributes in the referencing relation. The concept is described formally as: "For all tuples in the referencing relation projected over the referencing attributes, there must exist a tuple in the referenced relation projected over those same attributes such that

15318-594: The relevant part of the index fits into memory). Queries made against the relational database, and the derived relvars in the database are expressed in a relational calculus or a relational algebra . In his original relational algebra, Codd introduced eight relational operators in two groups of four operators each. The first four operators were based on the traditional mathematical set operations : The remaining operators proposed by Codd involve special operations specific to relational databases: Other operators have been introduced or proposed since Codd's introduction of

15456-399: The resolution table is then named appropriately and the two FKs are combined to form a PK. The migration of PKs to other tables is the second major reason why system-assigned integers are used normally as PKs; there is usually neither efficiency nor clarity in migrating a bunch of other types of columns. Relationships are a logical connection between different tables (entities), established on

15594-415: 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

15732-435: The same attributes . A tuple usually represents an object and information about that object. Objects are typically physical objects or concepts. A relation is usually described as a table , which is organized into rows and columns . All the data referenced by an attribute are in the same domain and conform to the same constraints. The relational model specifies that the tuples of a relation have no specific order and that

15870-442: The same operating system . With the advent of virtualization , the cluster nodes may run on separate physical computers with different operating systems which are painted above with a virtual layer to look similar. The cluster may also be virtualized on various configurations as maintenance takes place; an example implementation is Xen as the virtualization manager with Linux-HA . As the computer clusters were appearing during

16008-416: 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. An exclusive lock grants the user exclusive access to

16146-670: The same task, controlled and scheduled by software. The newest manifestation of cluster computing is cloud computing . The components of a cluster are usually connected to each other through fast local area networks , with each node (computer used as a server) running its own instance of an operating system . In most circumstances, all of the nodes use the same hardware and the same operating system, although in some setups (e.g. using Open Source Cluster Application Resources (OSCAR)), different operating systems can be used on each computer, or different hardware. Clusters are usually deployed to improve performance and availability over that of

16284-465: The scheduling and management of the slaves. In a typical implementation the Master has two network interfaces, one that communicates with the private Beowulf network for the slaves, the other for the general purpose network of the organization. The slave computers typically have their own version of the same operating system, and local memory and disk space. However, the private slave network may also have

16422-445: 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

16560-524: 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. 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

16698-424: 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

16836-460: The standard declarative SQL syntax. Stored procedures are not part of the relational database model, but all commercial implementations include them. An index is one way of providing quicker access to data. Indices can be created on any combination of attributes on a relation . Queries that filter using those attributes can find matching tuples directly using the index (similar to Hash table lookup), without having to check each tuple in turn. This

16974-475: The suspected node is disabled or powered off. For instance, power fencing uses a power controller to turn off an inoperable node. The resources fencing approach disallows access to resources without powering off the node. This may include persistent reservation fencing via the SCSI3 , fibre channel fencing to disable the fibre channel port, or global network block device (GNBD) fencing to disable access to

17112-446: The system to a stable state so that processing can resume without needing to recompute results. The Linux world supports various cluster software; for application clustering, there is distcc , and MPICH . Linux Virtual Server , Linux-HA – director-based clusters that allow incoming requests for services to be distributed across multiple cluster nodes. MOSIX , LinuxPMI , Kerrighed , OpenSSI are full-blown clusters integrated into

17250-479: The term has gradually come to describe a broader class of database systems, which at a minimum: In 1974, IBM began developing System R , a research project to develop a prototype RDBMS. The first system sold as an RDBMS was Multics Relational Data Store (June 1976). Oracle was released in 1979 by Relational Software, now Oracle Corporation . Ingres and IBM BS12 followed. Other examples of an RDBMS include IBM Db2 , SAP Sybase ASE , and Informix . In 1984,

17388-459: 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. SQL Server itself includes a Gatherer component that monitors changes to tables and invokes

17526-493: The threads entangled in a deadlock and roll back the transaction it started. 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

17664-456: The time. The MPI specifications then gave rise to specific implementations. MPI implementations typically use TCP/IP and socket connections. MPI is now a widely available communications model that enables parallel programs to be written in languages such as C , Fortran , Python , etc. Thus, unlike PVM which provides a concrete implementation, MPI is a specification which has been implemented in systems such as MPICH and Open MPI . One of

17802-559: The transformed data into destination databases or files. SQL Server Full Text Search service is a specialized indexing and querying service for unstructured text stored in SQL Server databases. 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 allows for inexact matching of

17940-767: The tuple contains a candidate or primary key then obviously it is unique; however, a primary key need not be defined for a row or record to be a tuple. The definition of a tuple requires that it be unique, but does not require a primary key to be defined. Because a tuple is unique, its attributes by definition constitute a superkey . All data are stored and accessed via relations . Relations that store data are called "base relations", and in implementations are called "tables". Other relations do not store data, but are computed by applying relational operations to other relations. These relations are sometimes called "derived relations". In implementations these are called " views " or "queries". Derived relations are convenient in that they act as

18078-473: The tuples, in turn, impose no order on the attributes. Applications access data by specifying queries, which use operations such as select to identify tuples, project to identify attributes, and join to combine relations. Relations can be modified using the insert , delete , and update operators. New tuples can supply explicit values or be derived from a query. Similarly, queries identify tuples for updating or deleting. Tuples by definition are unique. If

18216-401: The unique key of the linked row (such columns are known as foreign keys ). Codd showed that data relationships of arbitrary complexity can be represented by a simple set of concepts. Part of this processing involves consistently being able to select or modify one and only one row in a table. Therefore, most physical implementations have a unique primary key (PK) for each row in a table. When

18354-689: The values in each of the referencing attributes match the corresponding values in the referenced attributes." A stored procedure is executable code that is associated with, and generally stored in, the database. Stored procedures usually collect and customize common operations, like inserting a tuple into a relation , gathering statistical information about usage patterns, or encapsulating complex business logic and calculations. Frequently they are used as an application programming interface (API) for security or simplicity. Implementations of stored procedures on SQL RDBMS's often allow developers to take advantage of procedural extensions (often vendor-specific) to

18492-433: The world's fastest machine in 2011 was the K computer which has a distributed memory , cluster architecture. Greg Pfister has stated that clusters were not invented by any specific vendor but by customers who could not fit all their work on one computer, or needed a backup. Pfister estimates the date as some time in the 1960s. The formal engineering basis of cluster computing as a means of doing parallel work of any sort

18630-445: Was arguably invented by Gene Amdahl of IBM , who in 1967 published what has come to be regarded as the seminal paper on parallel processing: Amdahl's Law . The history of early computer clusters is more or less directly tied to the history of early networks, as one of the primary motivations for the development of a network was to link computing resources, creating a de facto computer cluster. The first production system designed as

18768-444: Was defined by E. F. Codd at IBM in 1970. Codd introduced the term relational in his research paper "A Relational Model of Data for Large Shared Data Banks". In this paper and later papers, he defined what he meant by relation . One well-known definition of what constitutes a relational database system is composed of Codd's 12 rules . However, no commercial implementations of the relational model conform to all of Codd's rules, so

18906-642: Was designed by a workgroup within IBM in the period 1988 to 1994. DRDA enables network connected relational databases to cooperate to fulfill SQL requests. The messages, protocols, and structural components of DRDA are defined by the Distributed Data Management Architecture . According to DB-Engines , in January 2023 the most popular systems on the db-engines.com web site were: According to research company Gartner , in 2011,

19044-615: Was released to General Availability in September 2018. Prior to release the preview version of the application was known as SQL Server Operations 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 . It

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