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Null (SQL)

Index Null (SQL)

Null (or NULL) is a special marker used in Structured Query Language to indicate that a data value does not exist in the database. [1]

81 relations: ACM Transactions on Database Systems, Aggregate function, Association for Computing Machinery, B-tree, Boolean data type, Check constraint, Christopher J. Date, Closed-world assumption, Co-NP-complete, Codd's 12 rules, Computerworld, Concatenation, Conditional (computer programming), Constant function, D (data language specification), Data definition language, Data domain, Data manipulation language, Data type, Database theory, Delete (SQL), Donald D. Chamberlin, Edgar F. Codd, Fabian Pascal, False dilemma, Foreign key, Function overloading, Functional completeness, Greek alphabet, Hugh Darwen, IBM System R, Imieliński-Lipski algebra, Insert (SQL), International Association of Engineers, Is functions, Join (SQL), Journal of the ACM, Law of excluded middle, Law of identity, Literal (computer programming), Microsoft SQL Server, MySQL, Null pointer, Omega, Open-world assumption, Partial equivalence relation, Pearson plc, PL/SQL, Possible world, PostgreSQL, ..., Procedural programming, Propositional calculus, Relational algebra, Relational database management system, Relational model, Relational Model/Tasmania, Reserved word, Reverse Polish notation, Select (SQL), Semipredicate problem, SIGMOD, Skolem normal form, SQL, SQL Server Compact, SQL syntax, SQL-92, SQL/PSM, SQL:1999, SQL:2003, SQLite, Structure (mathematical logic), Switch statement, Tautology (logic), Telephone number, The Third Manifesto, Three-valued logic, Tomasz Imieliński, Transact-SQL, Undefined value, Update (SQL), Where (SQL). Expand index (31 more) »

ACM Transactions on Database Systems

The ACM Transactions on Database Systems (ACM TODS) is one of the journals produced by the Association for Computing Machinery.

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Aggregate function

In database management an aggregate function is a function where the values of multiple rows are grouped together to form a single value of more significant meaning or measurement such as a set, a bag or a list.

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Association for Computing Machinery

The Association for Computing Machinery (ACM) is an international learned society for computing.

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In computer science, a B-tree is a self-balancing tree data structure that keeps data sorted and allows searches, sequential access, insertions, and deletions in logarithmic time.

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Boolean data type

In computer science, the Boolean data type is a data type that has one of two possible values (usually denoted true and false), intended to represent the two truth values of logic and Boolean algebra.

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Check constraint

A check constraint is a type of integrity constraint in SQL which specifies a requirement that must be met by each row in a database table.

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Christopher J. Date

Chris Date (born 1941) is an independent author, lecturer, researcher, and consultant, specializing in relational database theory.

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Closed-world assumption

The closed-world assumption (CWA), in a formal system of logic used for knowledge representation, is the presumption that a statement that is true is also known to be true.

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In complexity theory, computational problems that are co-NP-complete are those that are the hardest problems in co-NP, in the sense that any problem in co-NP can be reformulated as a special case of any co-NP-complete problem with only polynomial overhead.

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Codd's 12 rules

Codd's twelve rules are a set of thirteen rules (numbered zero to twelve) proposed by Edgar F. Codd, a pioneer of the relational model for databases, designed to define what is required from a database management system in order for it to be considered relational, i.e., a relational database management system (RDBMS).

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Computerworld is a publication website and digital magazine for information technology (IT) and business technology professionals.

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In formal language theory and computer programming, string concatenation is the operation of joining character strings end-to-end.

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Conditional (computer programming)

In computer science, conditional statements, conditional expressions and conditional constructs are features of a programming language, which perform different computations or actions depending on whether a programmer-specified boolean condition evaluates to true or false.

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Constant function

In mathematics, a constant function is a function whose (output) value is the same for every input value.

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D (data language specification)

D is a set of prescriptions for what Christopher J. Date and Hugh Darwen believe a relational database management system ought to be like.

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Data definition language

A data definition language or data description language (DDL) is a syntax similar to a computer programming language for defining data structures, especially database schemas.

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Data domain

In data management and database analysis, a data domain refers to all the values which a data element may contain.

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Data manipulation language

A data manipulation language (DML) is a computer programming language used for adding (inserting), deleting, and modifying (updating) data in a database.

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Data type

In computer science and computer programming, a data type or simply type is a classification of data which tells the compiler or interpreter how the programmer intends to use the data.

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Database theory

Database theory encapsulates a broad range of topics related to the study and research of the theoretical realm of databases and database management systems.

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Delete (SQL)

In the database structured query language (SQL), the DELETE statement removes one or more records from a table.

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Donald D. Chamberlin

Donald D. Chamberlin (born 21 December 1944) is an American computer scientist who is best known as one of the principal designers of the original SQL language specification with Raymond Boyce.

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Edgar F. Codd

Edgar Frank "Ted" Codd (19 August 1923 – 18 April 2003) was an English computer scientist who, while working for IBM, invented the relational model for database management, the theoretical basis for relational databases and relational database management systems.

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Fabian Pascal

Fabian Pascal is a consultant to large software vendors such as IBM, Oracle Corporation, and Borland, but is better known as an author and seminar speaker.

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False dilemma

A false dilemma is a type of informal fallacy in which something is falsely claimed to be an "either/or" situation, when in fact there is at least one additional option.

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Foreign key

In the context of relational databases, a foreign key is a field (or collection of fields) in one table that uniquely identifies a row of another table or the same table.

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Function overloading

In some programming languages, function overloading or method overloading is the ability to create multiple methods of the same name with different implementations.

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Functional completeness

In logic, a functionally complete set of logical connectives or Boolean operators is one which can be used to express all possible truth tables by combining members of the set into a Boolean expression.

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Greek alphabet

The Greek alphabet has been used to write the Greek language since the late 9th or early 8th century BC.

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Hugh Darwen

Hugh Darwen is a computer scientist who was an employee of IBM United Kingdom from 1967.

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IBM System R

IBM System R is a database system built as a research project at IBM's San Jose Research Laboratory beginning in 1974.

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Imieliński-Lipski algebra

An Imieliński-Lipski algebras is an extension of relational algebra onto tables with different types of null values.

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Insert (SQL)

An SQL INSERT statement adds one or more records to any single table in a relational database.

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International Association of Engineers

The International Association of Engineers (IAENG) is a non-profit international association for the engineers and the computer scientists.

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Is functions

The Is functions (also known as data information functions, data inspection functions, or data-testing functions) are a set of functions in Microsoft's Visual Basic 6, Visual Basic for Applications, VBScript, and Visual Basic.NET.

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Join (SQL)

An SQL join clause combines columns from one or more tables in a relational database.

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Journal of the ACM

The Journal of the ACM is a peer-reviewed scientific journal covering computer science in general, especially theoretical aspects.

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Law of excluded middle

In logic, the law of excluded middle (or the principle of excluded middle) states that for any proposition, either that proposition is true or its negation is true.

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Law of identity

In logic, the law of identity states that each thing is identical with itself.

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Literal (computer programming)

In computer science, a literal is a notation for representing a fixed value in source code.

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Microsoft SQL Server

Microsoft SQL Server is a relational database management system developed by Microsoft.

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MySQL ("My S-Q-L") is an open-source relational database management system (RDBMS).

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Null pointer

In computing, a null pointer has a value reserved for indicating that the pointer does not refer to a valid object.

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Omega (capital: Ω, lowercase: ω; Greek ὦ, later ὦ μέγα, Modern Greek ωμέγα) is the 24th and last letter of the Greek alphabet.

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Open-world assumption

In a formal system of logic used for knowledge representation, the open-world assumption is the assumption that the truth value of a statement may be true irrespective of whether or not it is known to be true.

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Partial equivalence relation

In mathematics, a partial equivalence relation (often abbreviated as PER, in older literature also called restricted equivalence relation) R on a set X is a relation that is symmetric and transitive.

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Pearson plc

Pearson plc is a British multinational publishing and education company headquartered in London.

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PL/SQL (Procedural Language/Structured Query Language) is Oracle Corporation's procedural extension for SQL and the Oracle relational database.

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Possible world

In philosophy and logic, the concept of a possible world is used to express modal claims.

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PostgreSQL, often simply Postgres, is an object-relational database management system (ORDBMS) with an emphasis on extensibility and standards compliance.

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Procedural programming

Procedural programming is a programming paradigm, derived from structured programming, based upon the concept of the procedure call.

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Propositional calculus

Propositional calculus is a branch of logic.

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Relational algebra

Relational algebra, first created by Edgar F. Codd while at IBM, is a family of algebras with a well-founded semantics used for modelling the data stored in relational databases, and defining queries on it.

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Relational database management system

A relational database management system (RDBMS) is a database management system (DBMS) based on the relational model invented by Edgar F. Codd at IBM's San Jose Research Laboratory.

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Relational model

The relational model (RM) for database management is an approach to managing data using a structure and language consistent with first-order predicate logic, first described in 1969 by Edgar F. Codd, where all data is represented in terms of tuples, grouped into relations.

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Relational Model/Tasmania

Relational Model/Tasmania (RM/T) was published by Edgar F. Codd in 1979 and is the name given to a number of extensions to his original relational model (RM) published in 1970.

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Reserved word

In a computer language, a reserved word (also known as a reserved identifier) is a word that cannot be used as an identifier, such as the name of a variable, function, or label – it is "reserved from use".

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Reverse Polish notation

Reverse Polish notation (RPN), also known as Polish postfix notation or simply postfix notation, is a mathematical notation in which operators follow their operands, in contrast to Polish notation (PN), in which operators precede their operands.

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Select (SQL)

The SQL SELECT statement returns a result set of records from one or more tables.

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Semipredicate problem

In computer programming, a semipredicate problem occurs when a subroutine intended to return a useful value can fail, but the signalling of failure uses an otherwise valid return value.

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SIGMOD is the Association for Computing Machinery's Special Interest Group on Management of Data, which specializes in large-scale data management problems and databases.

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Skolem normal form

In mathematical logic, a formula of first-order logic is in Skolem normal form if it is in prenex normal form with only universal first-order quantifiers.

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SQL (S-Q-L, "sequel"; Structured Query Language) is a domain-specific language used in programming and designed for managing data held in a relational database management system (RDBMS), or for stream processing in a relational data stream management system (RDSMS).

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SQL Server Compact

Microsoft SQL Server Compact (SQL CE) is a compact relational database produced by Microsoft for applications that run on mobile devices and desktops.

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SQL syntax

The syntax of the SQL programming language is defined and maintained by ISO/IEC SC 32 as part of ISO/IEC 9075.

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SQL-92 was the third revision of the SQL database query language.

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SQL/PSM (SQL/Persistent Stored Modules) is an ISO standard mainly defining an extension of SQL with a procedural language for use in stored procedures.

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SQL:1999 (also called SQL 3) was the fourth revision of the SQL database query language.

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SQL:2003 is the fourth revision of the SQL database query language.

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SQLite is a relational database management system contained in a C programming library.

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Structure (mathematical logic)

In universal algebra and in model theory, a structure consists of a set along with a collection of finitary operations and relations that are defined on it.

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Switch statement

In computer programming languages, a switch statement is a type of selection control mechanism used to allow the value of a variable or expression to change the control flow of program execution via a multiway branch.

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Tautology (logic)

In logic, a tautology (from the Greek word ταυτολογία) is a formula or assertion that is true in every possible interpretation.

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Telephone number

A telephone number is a sequence of digits assigned to a fixed-line telephone subscriber station connected to a telephone line or to a wireless electronic telephony device, such as a radio telephone or a mobile telephone, or to other devices for data transmission via the public switched telephone network (PSTN) or other private networks.

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The Third Manifesto

The Third Manifesto (1995) is Christopher J. Date's and Hugh Darwen's proposal for future database management systems, a response to two earlier Manifestos with the same purpose.

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Three-valued logic

In logic, a three-valued logic (also trinary logic, trivalent, ternary, or trilean, sometimes abbreviated 3VL) is any of several many-valued logic systems in which there are three truth values indicating true, false and some indeterminate third value.

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Tomasz Imieliński

Tomasz Imieliński (born July 11, 1954 in Toruń, Poland) is a Polish-American computer scientist, most known in the areas of data mining, mobile computing, data extraction, and search engine technology.

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Transact-SQL (T-SQL) is Microsoft's and Sybase's proprietary extension to the SQL (Structured Query Language) used to interact with relational databases.

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Undefined value

In computing (particularly, in programming), undefined value is a condition where an expression does not have a correct value, although it is syntactically correct.

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Update (SQL)

An SQL UPDATE statement changes the data of one or more records in a table.

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Where (SQL)

A WHERE clause in SQL specifies that a SQL Data Manipulation Language (DML) statement should only affect rows that meet specified criteria.

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C-table, COALESCE, Codd table, Codd tables, NULL (SQL), NULL marks, NULLIF, NVL, Null (database), SQL CASE, Sql case, Sql null, Uncertain database.


[1] https://en.wikipedia.org/wiki/Null_(SQL)

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