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Relational Database
A relational database is a digital database based on the relational model of data, as proposed by E. F. Codd in 1970.[1] A software system used to maintain relational databases is a relational database management system (RDBMS). Many relational database systems have an option of using the SQL (Structured Query Language) for querying and maintaining the database.[2] The term "relational database" was invented by E. F. Codd at IBM in 1970. Codd introduced the term in his research paper "A Relational Model of Data for Large Shared Data Banks".[3] In this paper and later papers, he defined what he meant by "relational". One well-known definition of what constitutes a relational database system is composed of Codd's 12 rules
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Primary Key
In the relational model of databases, a primary key is a specific choice of a minimal set of attributes (columns) that uniquely specify a tuple (row) in a relation (table).[a][1] Informally, a primary key is "which attributes identify a record", and in simple cases are simply a single attribute: a unique id. More formally, a primary key is a choice of candidate key (a minimal superkey); any other candidate key is an alternate key. A primary key may consist of real-world observables, in which case it is called a natural key, while an attribute created to function as a key and not used for identification outside the database is called a surrogate key
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Natural Key
A natural key (also known as business key[1]) is a type of unique key in a database formed of attributes that exist and are used in the external world outside the database (i.e. in the business domain or domain of discourse).[2] In the relational model of data, a natural key is a candidate key and is therefore a functional determinant for all attributes in a relation. A natural key is sometimes called domain key.[3] A natural key serves two complementary purposes: it provides a means of identification for data and it imposes a rule, specifically a uniqueness constraint, to ensure that data remains unique within an information system. The uniqueness constraint assures uniqueness of data within a certain technical context (e.g. a set of values in a table, file or relation variable) by rejecting input of any data that would otherwise violate the constraint
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Alternate Key
In the relational model of databases, a primary key is a specific choice of a minimal set of attributes (columns) that uniquely specify a tuple (row) in a relation (table).[a][1] Informally, a primary key is "which attributes identify a record", and in simple cases are simply a single attribute: a unique id. More formally, a primary key is a choice of candidate key (a minimal superkey); any other candidate key is an alternate key. A primary key may consist of real-world observables, in which case it is called a natural key, while an attribute created to function as a key and not used for identification outside the database is called a surrogate key
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Attribute (computing)
In computing, an attribute is a specification that defines a property of an object, element, or file. It may also refer to or set the specific value for a given instance of such. For clarity, attributes should more correctly be considered metadata. An attribute is frequently and generally a property of a property. However, in actual usage, the term attribute can and is often treated as equivalent to a property depending on the technology being discussed. An attribute of an object usually consists of a name and a value; of an element, a type or class name; of a file, a name and extension. For example, in computer graphics, line objects can have attributes such as thickness (with real values), color (with descriptive values such as brown or green or values defined in a certain color model, such as RGB), dashing attributes, etc
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Relvar
In relational databases, relvar is a term introduced by C. J. Date and Hugh Darwen as an abbreviation for relation variable in their 1995 paper The Third Manifesto, to avoid the confusion sometimes arising from the use of the term relation, by the inventor of the relational model, E. F. Codd, for a variable to which a relation is assigned as well as for the relation itself. The term is used in Date's well-known database textbook An Introduction to Database Systems and in various other books authored or coauthored by him. Relvar is not universally accepted as a term, and it is not used in the context of existing database management system products that support SQL[citation needed], whose counterpart concept (but not exact equivalent) is the base table, this being something that, like computer language variables in general, has a name and is subject to update (i.e., being assigned different values from time to time)
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MICRO Relational Database Management System
The MICRO Relational Database Management System was the first large-scale set-theoretic database management system to be used in production.[1] Though MICRO was initially considered to be an "Information Management System", it was eventually recognized to provide all the capabilities of an RDBMS. MICRO's major underpinnings and algorithms were based on the Set-Theoretic Data Structure (STDS) model developed by D. L. Childs of the University of Michigan's CONCOMP (Conversational Use of Computers) Project.[2][3][4] MICRO featured a natural language interface which allowed non-programmers to use the system.[5][6] Implementation of MICRO began in 1970 as part of the Labor Market Information System (LMIS) project at the University of Michigan's Institute of Labor and Industrial Relations (ILIR). Dr. Malcolm S
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One-to-one (data Model)
In systems analysis, a one-to-one relationship is a type of cardinality that refers to the relationship between two entities (see also entity–relationship model) A and B in which one element of A may only be linked to one element of B, and vice versa. In mathematical terms, there exists a bijective function from A to B. For instance, think of A as the set of all human beings, and B as the set of all their brains. Any person from A can and must have only one brain from B, and any human brain in B can and must belong to only one person that is contained in A. In a relational database, a one-to-one relationship exists when one row in a table may be linked with only one row in another table and vice versa. It is important to note that a one-to-one relationship is not a property of the data, but rather of the relationship itself
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