DBMS: Key (Definitions)

"A field used to identify a record, often used as the index field for a table." (Karen Paulsell et al, "Sybase SQL Server: Performance and Tuning Guide", 1996)

"A column or group of columns that uniquely identifies a row (PRIMARY KEY), defines the relationship between two tables (FOREIGN KEY), or is used to build an index." (Microsoft Corporation, "SQL Server 7.0 System Administration Training Kit", 1999)

"A data element (attribute or column) or the combination of several used to identify a member of a set, instance of an entity, or record in a table." (Sharon Allen & Evan Terry, "Beginning Relational Data Modeling" 2nd Ed., 2005)

"A data item or combination of data items used to identify or locate a record instance (or other similar data groupings)." (William H Inmon, "Building the Data Warehouse", 2005)

"A specialized field determining uniqueness, or application of referential integrity through use of primary and foreign keys." (Gavin Powell, "Beginning Database Design", 2006)

"Key is a data item that helps to identify individual occurrences of an entity type." (S. Sumathi & S. Esakkirajan, "Fundamentals of Relational Database Management Systems", 2007)

"A column or group of columns that uniquely identifies a row (primary key), defines the relationship between two tables (foreign key), or is used to build an index." (Jim Joseph et al, "Microsoft SQL Server 2008 Reporting Services Unleashed", 2009)

"A generic term for a set of one or more attributes (data items) that, taken collectively, enables one to identify uniquely an entity or a record in a SQL table; a superkey." (Toby J Teorey, ", Database Modeling and Design" 4th Ed., 2010)

"A data item or combination of data items designated to uniquely identify a particular entity instance or table row." (DAMA International, "The DAMA Dictionary of Data Management", 2011)

"An entity identifier based on the concept of functional dependence; may be classified as follows: Superkey - an attribute (or combination of attributes) that uniquely identifies each entity in a table. Candidate key - a minimal superkey, that is, one that does not contain a subset of attributes that is itself a superkey. Primary key (PK) - a candidate key selected as a unique entity identifier." (Carlos Coronel et al, "Database Systems: Design, Implementation, and Management" 9th Ed., 2011)

"A column or group of columns that uniquely identifies a row (primary key), defines the relationship between two tables (foreign key), or is used to build an index." (Microsoft, "SQL Server 2012 Glossary", 2012)

"The attributes that identify entity occurrences and define relationships between entities." (Craig S Mullins, "Database Administration", 2012)

"An identifying attribute of data" (Daniel Linstedt & W H Inmon, "Data Architecture: A Primer for the Data Scientist", 2014)

"In a relational database, a set of one or more fields that uniquely identifies a record." (Rod Stephens, "Beginning Software Engineering", 2015)

"In key-value databases, a key is a reference to a value. In relational databases, a key is also a way to reference a row in a table. Primary keys refer to the way of uniquely identifying a row. Foreign keys refer to keys stored in one table that are used to reference rows in other tables." (Dan Sullivan, "NoSQL for Mere Mortals®", 2015)

"One or more fields of a database record that uniquely identifies it among all other records in the table." (Nell Dale & John Lewis, "Computer Science Illuminated" 6th Ed., 2015)

"Sequence of bits that are used as instructions that govern the acts of cryptographic functions within an algorithm." (Adam Gordon, "Official (ISC)2 Guide to the CISSP CBK" 4th Ed., 2015)

"A column or an ordered collection of columns that is identified in the description of an index, unique constraint, or referential constraint. An index key can also be an expression, an ordered collection of expressions, or an ordered collection of columns and expressions." (Sybase, "Open Server Server-Library/C Reference Manual", 2019)

"A subset of row data that uniquely identifies a row. Key data uniquely describes the current row in an open cursor." (Sybase, "Open Server Server-Library/C Reference Manual", 2019)