🛢DBMS: Roll Forward (Definitions)

"To recover from disasters, such as media failure, by reading the transaction log and reapplying all readable and complete transactions. See also roll back." (Microsoft Corporation, "SQL Server 7.0 System Administration Training Kit", 1999)

"To apply all the completed transactions from a database or log backup in order to recover a database to a point in time or the point of failure." (Anthony Sequeira & Brian Alderman, "The SQL Server 2000 Book", 2003)

"To apply logged changes to data in a roll forward set to bring the data forward in time." (Thomas Moore, "MCTS 70-431: Implementing and Maintaining Microsoft SQL Server 2005", 2006)

"The process of applying committed transactions. As a part of the recovery process, committed transactions are rolled forward to ensure the database is recovered in a consistent state with the changed data in the database." (Darril Gibson, "MCITP SQL Server 2005 Database Developer All-in-One Exam Guide", 2008)

"To apply logged changes to the data in a roll forward set to bring the data forward in time." (SQL Server 2012 Glossary, "Microsoft", 2012)

"To update the data in a restored database or table space by applying changes recorded in the database log files." (Sybase, "Open Server Server-Library/C Reference Manual", 2019)

🛢DBMS: Roll Back (Definitions)

"To remove partially completed transactions after a database or other system failure." (Microsoft Corporation, "SQL Server 7.0 System Administration Training Kit", 1999)

"To reverse changes made by transactions that were uncommitted at the point in time to which a database is being recovered." (Thomas Moore, "MCTS 70-431: Implementing and Maintaining Microsoft SQL Server 2005", 2006)

"To reverse or undo changes made so far." (Marilyn Miller-White et al, "MCITP Administrator: Microsoft® SQL Server™ 2005 Optimization and Maintenance 70-444", 2007)

"The process of undoing uncommitted transactions. As a part of the recovery process, uncommitted transactions are rolled back to ensure the database is recovered in a consistent state." (Darril Gibson, "MCITP SQL Server 2005 Database Developer All-in-One Exam Guide", 2008)

"Undo the changes made by a transaction, restoring the database to the state it was in before the transaction began." (Jan L Harrington, "Relational Database Design and Implementation" 3rd Ed., 2009)

"End a transaction, undoing any changes made by the transaction and restoring the database to the state it was in before the transaction began." (Jan L Harrington, "SQL Clearly Explained" 3rd Ed., 2010)

"To reverse changes." (Microsoft, "SQL Server 2012 Glossary", 2012)

"To undo the database statements performed prior to a commit of the transaction." (Craig S Mullins, "Database Administration", 2012)

"To restore data that is changed by an SQL statement to the state at its last commit point." (IBM, "Informix Servers 12.1", 2014)

"To return to a previous version, as in rolling back a device driver." (Faithe Wempen, "Computing Fundamentals: Introduction to Computers", 2015)

"To restore data that is changed by an SQL statement to the state at its last commit point." (Sybase, "Open Server Server-Library/C Reference Manual", 2019)

 "To return the values changed by a transaction to their original state." (Microsoft, "ODBC Glossary")

🛢DBMS: Index Selectivity (Definitions)

"The ratio of duplicate key values in an index. An index is selective when it lets the optimizer pinpoint a single row, such as a search for a unique key. An index on nonunique entries is less selective. An index on values such as 'M' or 'F' (for male or female) is extremely nonselective." (Karen Paulsell et al, "Sybase SQL Server: Performance and Tuning Guide", 1996)

"A ratio of the number of rows accessed for a query to die total number of rows in a table." (Owen Williams, "MCSE TestPrep: SQL Server 6.5 Design and Implementation", 1998)

"The number of distinct values divided by the total number of values. For example, if the values are {A,A,B,B} then the number of distinct values, that is, the number that a SELECT DISTINCT . . . statement would return, is two, while the total number of values is four.  So selectivity is 2/4 in this case. Selectivity is usually expressed as a percentage ('selectivity is 50%'), but some express it as a ratio ('selectivity is 0.5') instead. " (Peter Gulutzan & Trudy Pelzer, "SQL Performance Tuning", 2002)

"This is a term used to describe the number of duplicate values in a column." (Joseph L Jorden & Dandy Weyn, "MCTS Microsoft SQL Server 2005: Implementation and Maintenance Study Guide - Exam 70-431", 2006)

"The degree of unique values for the data contained in a table column." (Victor Isakov et al, "MCITP Administrator: Microsoft SQL Server 2005 Optimization and Maintenance (70-444) Study Guide", 2007)

"A measure of how likely an index will be used in query processing." (Carlos Coronel et al, "Database Systems: Design, Implementation, and Management" 9th Ed., 2011)

"A value indicating the proportion of a row set retrieved by a predicate or combination of predicates, for example, WHERE last_name = 'Smith'. A selectivity of 0 means that no rows pass the predicate test, whereas a value of 1 means that all rows pass the test.  The adjective selective means roughly "choosy." Thus, a highly selective query returns a low proportion of rows (selectivity close to 0), whereas an unselective query returns a high proportion of rows (selectivity close to 1)." (Oracle, "Database SQL Tuning Guide Glossary", 2013)

[selectivity function:] "A function that calculates the percentage of rows that will be returned by a filter function in the WHERE clause of a query. The optimizer uses selectivity information to determine the fastest way to execute an SQL query." (IBM, "Informix Servers 12.1", 2014)

"The probability that any table row will satisfy a predicate." (IBM, "Informix Servers 12.1", 2014)

"A property of data distribution, the number of distinct values in a column (its cardinality) divided by the number of records in the table. High selectivity means that the column values are relatively unique, and can retrieved efficiently through an index. If you (or the query optimizer) can predict that a test in a WHERE clause only matches a small number (or proportion) of rows in a table, the overall query tends to be efficient if it evaluates that test first, using an index." (MySQL, "MySQL 8.0 Reference Manual Glossary")

"In a query, the measure of how many rows from a row set pass a predicate test, for example, WHERE last_name = 'Smith'. A selectivity of 0.0 means no rows, whereas a value of 1.0 means all rows. A predicate becomes more selective as the value approaches 0.0 and less selective (or more unselective) as the value approaches 1.0." (Oracle, "Oracle Database Concepts", 0)

🛢DBMS: Surrogate Key (Definitions)

"A unique identifier for a row within a database table. A surrogate, or candidate, key can be made up of one or more columns. By definition, every table must have at least one surrogate key (in which case it becomes the primary key for a table automatically). However, it is possible for a table to have more than one surrogate key (in which case one of them must be designated as the primary key). Any surrogate key that is not the primary key is called the alternate key." (Microsoft Corporation, "SQL Server 7.0 System Administration Training Kit", 1999)

"A primary key that is typically invisible to the end user. Normally, surrogate keys are used where end users have their own pre-existing identification schemes (such as an ISBN in a database of books), so the users can modify their existing identifiers." (Bill Pribyl & Steven Feuerstein, "Learning Oracle PL/SQL", 2001)

"Integer keys that are sequentially assigned as needed in the staging area to populate a dimension table and join to the fact table. In the dimension table, the surrogate key is the primary key. In the fact table, the surrogate key is a foreign key to a specific dimension and may be part of the fact table’s primary key, although this is not required. A surrogate key usually cannot be interpreted by itself. That is, it is not a smart key in any way. Surrogate keys are required in many data warehouse situations to handle slowly changing dimensions, as well as missing or inapplicable data. Also known as artificial keys, integer keys, meaningless keys, non-natural keys, and synthetic keys." (Ralph Kimball & Margy Ross, "The Data Warehouse Toolkit" 2nd Ed., 2002)

"A surrogate key is a substitute key that is usually an arbitrary numeric value assigned by the load process or the database system. The advantage of the surrogate key is that it can be structured so that it is always unique throughout the span of integration for the data warehouse." (Claudia Imhoff et al, "Mastering Data Warehouse Design", 2003)

"A single-part, artificially established identifier for an entity. Surrogate key assignment is a special case of derived data - one where the primary key is derived. A common way of deriving surrogate key values is to assign integer values sequentially." (Sharon Allen & Evan Terry, "Beginning Relational Data Modeling" 2nd Ed., 2005)

[artificial key:] "A system-generated, nonsignificant, surrogate identifier or globally unique identifier (GUID) used to uniquely identify a row in a table. This is also known as a surrogate key." (Sharon Allen & Evan Terry, "Beginning Relational Data Modeling" 2nd Ed., 2005)

"A redundant, unique key generated for a record in a data warehouse table to allow integration of data from multiple source systems and to support changing data over time." (Reed Jacobsen & Stacia Misner, "Microsoft SQL Server 2005 Analysis Services Step by Step", 2006)

"The primary key column of a dimension table. The surrogate key is unique to the data warehouse. Key values have no intrinsic meaning, and are assigned as part of the ETL process. By avoiding the use of a natural key, the data warehouse is able to handle changes to operational data in a different manner from transaction systems. The use of a surrogate key also eliminates the need to join fact and dimension tables via multi-part keys." (Christopher Adamson, "Mastering Data Warehouse Aggregates", 2006)

"Used as a replacement or substitute for a descriptive primary key, allowing for better control, better structure, less storage space, more efficient indexing, and absolute surety of uniqueness. Surrogate keys are usually integers, and usually automatically generated using auto counters or sequences." (Gavin Powell, "Beginning Database Design", 2006)

"An artificial key field, usually with system-assigned sequential numbers, used in the dimensional model to link a dimension table to the fact table. In a dimension table, the surrogate key is the primary key which becomes a foreign key in the fact table." (Paulraj Ponniah, "Data Warehousing Fundamentals for IT Professionals", 2010)

"A single-part, artificially established, physical identifier for a data set, usually not visible to business users, and used for database management and performance. Surrogate key assignment is a special case of derived data - one where the primary key is derived. A common way of deriving surrogate key values is to assign integer values sequentially. Sometimes referred to as a dummy key, sequential key, or auto-number field." (DAMA International, "The DAMA Dictionary of Data Management", 2011)

"A system-assigned primary key, generally numeric and auto-incremented." (Carlos Coronel et al, "Database Systems: Design, Implementation, and Management" 9th Ed., 2011)

🛢DBMS: Alternate Key (Definitions)

"Column or combination of columns, not the primary key columns, whose values uniquely identify a row in a table." (Sharon Allen & Evan Terry, "Beginning Relational Data Modeling 2nd Ed.", 2005)

"A candidate key that is not used as the table's primary key." (Rod Stephens, "Beginning Database Design Solutions", 2008)

"Unique identifier for an entity instance other than the primary key." (Craig S Mullins, "Database Administration", 2012)

"Other columns that could be used as a primary key but are not implemented as such." (Owen Williams, "MCSE TestPrep: SQL Server 6.5 Design and Implementation", 1998)

"In relational theory, any unique key that is not a primary key." (David C Hay, "Data Model Patterns: A Metadata Map", 2010)

🛢DBMS: Composite Key (Definitions)

"An index key that includes two or more columns; for example, authors(au_lname, au_fname)." (Karen Paulsell et al, "Sybase SQL Server: Performance and Tuning Guide", 1996)

"A key composed of two or more columns. A drawback of composite keys is that they require more complex joins when two or more tables are joined." (Microsoft Corporation, "SQL Server 7.0 System Administration Training Kit", 1999)

"Key in a database table made up of several columns. Same as Concatenated key. The overall key in a typical fact table is a subset of the foreign keys in the fact table. In other words, it usually does not require every foreign key to guarantee uniqueness of a fact table row." (Ralph Kimball & Margy Ross, "The Data Warehouse Toolkit" 2nd Ed., 2002)

"A key composed of two or more columns." (Anthony Sequeira & Brian Alderman, "The SQL Server 2000 Book", 2003)

"A candidate key made up of more than one attribute or column." (Sharon Allen & Evan Terry, "Beginning Relational Data Modeling" 2nd Ed., 2005)

"A primary key, unique key, or foreign key consisting of more than one field." (Gavin Powell, "Beginning Database Design", 2006)

"Multiple key columns used to uniquely identify a record." (Reed Jacobsen & Stacia Misner, "Microsoft SQL Server 2005 Analysis Services Step by Step", 2006)

"A candidate key comprising more than one attribute." (S. Sumathi & S. Esakkirajan, "Fundamentals of Relational Database Management Systems", 2007)

"A key that includes two or more fields. Also called a compound key or concatenated key." (Rod Stephens, "Beginning Database Design Solutions", 2008)

"A key for a database table made up of more than one attribute or field." (Paulraj Ponniah, "Data Warehousing Fundamentals for IT Professionals", 2010)

"A key whose definition consists of two or more fields in a file, columns in a table, or attributes in a relation." (Microsoft, "SQL Server 2012 Glossary", 2012)

"A key with more than one attribute." (Craig S Mullins, "Database Administration", 2012)

"An ordered set of key columns or expressions where the referenced column names are from the same table. See also key." (Sybase, "Open Server Server-Library/C Reference Manual", 2019)

🛢DBMS: Candidate Key (Definitions)

"A unique identifier for a row within a database table. A candidate, or surrogate, key can be made up of one or more columns. In a normalized database, every table must have at least one candidate key, in which case it is considered the primary key for a table automatically. However, it is possible for a table to have more than one candidate key, in which case one of them must be designated as the primary key. Any candidate key that is not the primary key is called the alternate key." (Microsoft Corporation, "SQL Server 7.0 System Administration Training Kit", 1999)

"Any attribute or group of attributes that uniquely identifies each instance of an entity and that’s a possible choice for the primary key." (Sharon Allen & Evan Terry, "Beginning Relational Data Modeling" 2nd Ed., 2005)

"Also known as a potential key, or permissible key. A field or combination of fields, which can act as a primary key field for a table. A candidate key uniquely identifies each record in the table." (Gavin Powell, "Beginning Database Design", 2006)

"Any data item or group of data items which identify uniquely tuples in a relation." (S. Sumathi & S. Esakkirajan, "Fundamentals of Relational Database Management Systems", 2007)

"A minimal superkey. In other words, the fields in a candidate key uniquely define the records in a table and no subset of those fields also uniquely defines the records." (Rod Stephens, "Beginning Database Design Solutions", 2008)

"Any subset of the attributes (data items) in a superkey that is also a superkey and is not reducible to another superkey." (Toby J Teorey, ", Database Modeling and Design" 4th Ed., 2010)

"A column or set of columns that have a unique value for each row in a table." (Microsoft, "SQL Server 2012 Glossary", 2012)

"An attribute or set of attributes that can be used to uniquely identify an occurrence of the entity. Each entity may have one or more candidate keys. One of these candidate keys is selected as the table primary key." (Craig S Mullins, "Database Administration", 2012)

"A column or combination of columns that can be used as the primary key of a relation." (Jan L Harrington, "Relational Database Design and Implementation" 3rd Ed., 2009)

🛢DBMS: Role (Definitions)

"Provide individual accountability for users performing system administration and security-related tasks in SQL Server. The System Administrator, System Security Officer, and Operator roles can be granted to individual server login accounts." (Karen Paulsell et al, "Sybase SQL Server: Performance and Tuning Guide", 1996)

"An administrative unit within SQL Server that contains SQL Server logins, Windows NT logins, groups, or other roles." (Microsoft Corporation, "SQL Server 7.0 System Administration Training Kit", 1999)

"In Oracle, a named database object that can receive privileges and in turn be granted to accounts. Simplifies administration of privileges." (Bill Pribyl & Steven Feuerstein, "Learning Oracle PL/SQL", 2001)

"A security account that is a collection of other security accounts that can be treated as a single unit when managing permissions. A role can contain SQL Server logins, other roles, and Windows logins or groups." (Anthony Sequeira & Brian Alderman, "The SQL Server 2000 Book", 2003)

"A group of related privileges that is referenced by a single name. Privileges can be assigned to a role, and a role can be assigned to a database user or to another role. Roles ease the maintenance issues with managing privileges for a large number of users who can be grouped into a relatively small number of categories based on job function." (Bob Bryla, "Oracle Database Foundations", 2004)

"A SQL Server security account is a collection of other security accounts that can be treated as a single unit when managing permissions. A role can contain SQL Server logins, other roles, and Windows logins or groups." (Thomas Moore, "EXAM CRAM™ 2: Designing and Implementing Databases with SQL Server 2000 Enterprise Edition", 2005)

"A definition of security permissions for one or more user accounts or user groups defined in the operating system and applied to an OLAP database or cube." (Reed Jacobsen & Stacia Misner, "Microsoft SQL Server 2005 Analysis Services Step by Step", 2006)

"A set of privileges that permit actions on specified resources. Roles assigned to a user determine the user’s access to resources and operations." (MongoDb, "Glossary", 2008)

"Roles exist at both the server level and the database level. By adding logins to roles, they are automatically granted the permissions of that role. For example, by adding a user to the sysadmin role, the user can do anything on the instance of the server. By adding a user to the dbowner role, the user can do anything in the database." (Darril Gibson, "MCITP SQL Server 2005 Database Developer All-in-One Exam Guide", 2008)

"In Oracle, a named collection of database access privileges that authorize a user to connect to a database and use the database system resources." (Carlos Coronel et al, "Database Systems: Design, Implementation, and Management" 9th Ed., 2011)

"(1) Name used to refer to the logical set of related responsibilities assignable to a person or organization, and to parties with these assigned responsibilities. (2) A database security mechanism used to grant one or more preassigned privileges to a user." (Craig S Mullins, "Database Administration", 2012)

"A database entity that groups together one or more privileges and that can be assigned, for example, to users, PUBLIC, other roles, or trusted contexts." (Sybase, "Open Server Server-Library/C Reference Manual", 2019)

🛢DBMS: Covering Index (Definitions)

 [index covering]"A data access condition where the leaf-level pages of a nonclustered index contain the data needed to satisfy a query. The index must contain all columns in the select list as well as the columns in the query clauses, if any. The server can satisfy the query using only the leaf level of the index. When an index covers a query, the server does not access the data pages." (Karen Paulsell et al, "Sybase SQL Server: Performance and Tuning Guide", 1996)

"A nonclustered index that contains all of the columns required to satisfy a query, in both the selection list and the WHERE clause." (Microsoft Corporation, "SQL Server 7.0 System Administration Training Kit", 1999)

"An index that contains every column in the select list of a query." (Peter Gulutzan & Trudy Pelzer, "SQL Performance Tuning", 2002)

"An index where the values of the data are stored in the index, allowing data retrieval from the index itself, instead of the data object." (DAMA International, "The DAMA Dictionary of Data Management", 2011)

🛢DBMS: Foreign Key [FK] (Definitions)

"A key column in a table that logically depends on a primary key column in another table. Also, a column (or combination of columns) whose values are required to match a primary key in some other table." (Karen Paulsell et al, "Sybase SQL Server: Performance and Tuning Guide", 1996)

"The column or combination of columns whose values match the primary key (PK) or unique key in the same or another table. A foreign key does not have to be unique. A foreign key is often in a many-to-one relationship with a primary key. Foreign key values should be copies of the primary key values; no value in the foreign key except NULL should ever exist unless the same value exists in the primary key. A foreign key may be NULL; if any part of a composite foreign key is NULL, the entire foreign key must be NULL." (Microsoft Corporation, "SQL Server 7.0 System Administration Training Kit", 1999)

"A type of constraintthat enforces a logical relationshipbetween a row in one table and one or more rows in another table. Often, this is a master-detail relationship, where the primary key value of a row in one table appears in the "foreign key" column of one or more rows in another table." (Bill Pribyl & Steven Feuerstein, "Learning Oracle PL/SQL", 2001)

"A column in a relational database table whose values are drawn from the values of a primary key in another table. In a star-join schema, the components of a composite fact table key are foreign keys with respect to each of the dimension tables." (Ralph Kimball & Margy Ross, "The Data Warehouse Toolkit" 2nd Ed., 2002)

"A column or combination of columns whose values match the primary key (PK) or unique key in another table. The foreign key is also called the referencing key in some literature." (Anthony Sequeira & Brian Alderman, "The SQL Server 2000 Book", 2003)

"A column (or columns) in a table that draws its values from a primary or unique key column in another table. A foreign key assists in ensuring the data integrity of a table." (Bob Bryla, "Oracle Database Foundations", 2004)

"A column or multiple columns whose values match the Primary Key of another table. Foreign Keys help in the relational process between two entities by connecting the foreign attribute in the child entity to a Primary Key in a parent entity." (Thomas Moore, "EXAM CRAM™ 2: Designing and Implementing Databases with SQL Server 2000 Enterprise Edition", 2005)

"Column or combination of columns whose values are required to match a primary key in some other table." (Sharon Allen & Evan Terry, "Beginning Relational Data Modeling" 2nd Ed., 2005)

"A type of constraint where columns contain copies of primary key values, uniquely identified in parent entities, representing the child or sibling side of what is most commonly a one-to-many relationship." (Gavin Powell, "Beginning Database Design", 2006)

"Attribute or set of attributes that identifies the entity with which another entity is associated." (S. Sumathi & S. Esakkirajan, "Fundamentals of Relational Database Management Systems", 2007)

"Used to maintain relationships between entities. Implemented as a field in a child table that has a corresponding primary key that it references." (Marilyn Miller-White et al, "MCITP Administrator: Microsoft® SQL Server™ 2005 Optimization and Maintenance 70-444", 2007)

"An FK is used to create a relationship between two tables, and typically points to a PK (PRIMARY KEY) in another table. The relationship enforces integrity between the two tables, allowing only entries in the FK table that exist in the PK table, and preventing deletions from the PK table if a related entry exists in the FK table." (Darril Gibson, "MCITP SQL Server 2005 Database Developer All-in-One Exam Guide", 2008)

"Information that establishes a relationship between two tables. By preventing erroneous data modifications, this association helps preserve data integrity." (Robert D. Schneider & Darril Gibson, "Microsoft SQL Server 2008 All-In-One Desk Reference For Dummies", 2008)

"One or more columns that are related to values in corresponding columns in another table." (Rod Stephens, "Beginning Database Design Solutions", 2008)

"An attribute (or combination of attributes) in a relation that is the same as the primary key of another relation. A foreign key may be a non-key attribute in its own relation, or it may be part of a concatenated primary key." (Jan L Harrington, "Relational Database Design and Implementation" 3rd Ed., 2009)

"The column or combination of columns whose values match the primary key (PK) or unique key in the same or another table." (Jim Joseph, "Microsoft SQL Server 2008 Reporting Services Unleashed", 2009)

"An attribute in a relational table used for establishing the direct relationship with another table, known as the parent table. The values for the foreign key attribute are drawn from the primary key values of the parent table." (Paulraj Ponniah, "Data Warehousing Fundamentals for IT Professionals", 2010)

"Any attribute in a SQL table (key or nonkey) that is taken from the same domain of values as the primary key in another SQL table and can be used to join the two tables (without loss of data integrity) as part of a SQL query." (Toby J Teorey, ", Database Modeling and Design" 4th Ed., 2010)

"1.An attribute (or attributes) in a relational table which is from the same domain as the identifier of the same or another table; can be thought of as a logical pointer from the “referencing” entity table (with the foreign key) to the “referenced” entity table (with the identifier). It is used to represent a many-to-one relationship between the referencing and referenced tables. It is not necessary for a foreign key to have a value; that is determined by the independently defined dependency characteristic. 2.The preferred primary key of a parent data subject that is placed in a subordinate data subject to identify the relevant parent data occurrence in that parent data subject." (DAMA International, "The DAMA Dictionary of Data Management", 2011)

"Field whose purpose is to link two or more tables together." (Linda Volonino & Efraim Turban, "Information Technology for Management 8th Ed", 2011)

"A key in a database table that comes from another table (also know as the "referenced table") and whose values match the primary key (PK) or unique key in the referenced table." (Microsoft, "SQL Server 2012 Glossary", 2012)

"An attribute or set of attributes that identify relationships between entity occurrences." (Craig S Mullins, "Database Administration", 2012)

"One or more attributes that are included in one entity for the purpose of identifying another." (James Robertson et al, "Complete Systems Analysis: The Workbook, the Textbook, the Answers", 2013)

"An attribute used for distinguishing a record that participates in a relationship with another table" (Daniel Linstedt & W H Inmon, "Data Architecture: A Primer for the Data Scientist", 2014)

"A field that has a relationship to the primary key field in another table." (Faithe Wempen, "Computing Fundamentals: Introduction to Computers", 2015)

"An attribute of one table that is related to the primary key of another table." (Adam Gordon, "Official (ISC)2 Guide to the CISSP CBK" 4th Ed., 2015)

"In a relational database, a set of one or more fields in one table with values that uniquely define a record in another table. The table containing the foreign key is the child table, and the table that contains the uniquely identified record is the parent table." (Rod Stephens, "Beginning Software Engineering", 2015)

"A column or set of columns that refers to a parent key. In a relational database, a key in one table that references the primary key in another table. See also constraint, primary key, unique key." (Sybase, "Open Server Server-Library/C Reference Manual", 2019)

🛢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)

🛢DBMS: Primary Key [PK] (Definitions)

"The column or columns whose values uniquely identify a row in a table." (Karen Paulsell et al, "Sybase SQL Server: Performance and Tuning Guide", 1996)

"The column or combination of columns that uniquely identifies a table. It must always be non-null and will always have a unique index. A primary key is used for joins with foreign keys in other tables." (Patrick Dalton, "Microsoft SQL Server Black Book", 1997)

"A column (or columns) in a table that makes the row in the table distinguishable from every other row in the same table." (Bob Bryla, "Oracle Database Foundations", 2004)

"A column or set of columns that uniquely identify all the rows in a table." (Thomas Moore, "EXAM CRAM™ 2: Designing and Implementing Databases with SQL Server 2000 Enterprise Edition", 2005)

"A unique attribute used to identify a single record in a database." (William H Inmon, "Building the Data Warehouse", 2005)

"This is an index that ensures that each of the records in your table is unique in  some way." (Joseph L Jorden & Dandy Weyn, "MCTS Microsoft SQL Server 2005: Implementation and Maintenance Study Guide - Exam 70-431", 2006)

"A candidate key that is singled out as the table's 'main' method for uniquely identifying records. Most databases automatically build an index for a table's primary key and enforce uniqueness." (Rod Stephens, "Beginning Database Design Solutions", 2008)

"In relational theory, the set of columns whose values can be used to uniquely identify each row (tuple in Dr. Codd’s original terminology) in a table (relation to Dr. Codd)." (David C Hay, "Data Model Patterns: A Metadata Map", 2010)

"The unique key (normally) used for creating foreign keys pointing to the subject table from other tables." (David C Hay, "Data Model Patterns: A Metadata Map", 2010)

"A set of one or more data attributes whose values are used to uniquely identify an entity instance or relational database table row. The primary key will have a unique value for each record or row in the table and is the means of navigation across entities and tables. Primary key attributes and values of parent entities and tables appear as foreign key attributes and values in child entities and tables." (DAMA International, "The DAMA Dictionary of Data Management", 2011)

"The attribute, or set of attributes, that is used to uniquely identify an occurrence of the entity. Each entity must have one and only one primary key." (Craig S Mullins, "Database Administration", 2012)

🛢DBMS: Data Integrity (Definitions)

"The correctness and completeness of data within a database." (Karen Paulsell et al, "Sybase SQL Server: Performance and Tuning Guide", 1996)

"A general term that refers to the correctness of the data contained in a database." (Owen Williams, "MCSE TestPrep: SQL Server 6.5 Design and Implementation", 1998)

"The accuracy and reliability of data. Data integrity is important in both single-user and multiuser environments. In multiuser environments, where data is shared, both the potential for and the cost of data corruption are high. In large-scale relational database management system (RDBMS) environments, data integrity is a primary concern." (Microsoft Corporation, "SQL Server 7.0 System Administration Training Kit", 1999)

"Data integrity refers to a state in which all the data values stored in the database are correct." (Anthony Sequeira & Brian Alderman, "The SQL Server 2000 Book", 2003)

"The condition that exists when there’s no accidental or intentional destruction, alteration, or loss of data." (Sharon Allen & Evan Terry, "Beginning Relational Data Modeling" 2nd Ed., 2005)

"The bits of data that are put in storage (via I/O writes) are the same bits of data—order and completeness - that come out (via I/O reads)." (David G Hill, "Data Protection: Governance, Risk Management, and Compliance", 2009)

"In a relational database, refers to a condition in which the data in the database is in compliance with all entity and referential integrity constraints." (Carlos Coronel et al, "Database Systems: Design, Implementation, and Management 9th Ed", 2011)

"The accuracy of data and its conformity to its expected value, especially after being transmitted or processed." (Microsoft, "SQL Server 2012 Glossary", 2012)

"Refers to the accuracy and quality of the data." (Steve Conger, "Hands-on database : an introduction to database design and development", 2012)

"Data integrity is the state of data being free from corruption." (Vince Buffalo, "Bioinformatics Data Skills", 2015)

"The property that data has not been altered in an authorized manner." (O Sami Saydjari, "Engineering Trustworthy Systems: Get Cybersecurity Design Right the First Time", 2018)

"The degree to which the data is internal or referential/consistent. If the key to refer to a different table is invalid, the join between the two tables cannot be made." (Piethein Strengholt, "Data Management at Scale", 2020)

"(1) In the context of data and network security: The assurance that information can only be accessed or modified by those authorized to do so. (2) In the context of data quality: The assurance the data are clean, traceable, and fit for purpose." (CODATA)

"The degree to which a collection of data is complete, consistent, and accurate. See also: data security; database integrity; integrity." (IEEE 610.5-1990)

🛢DBMS: Atomic(-level) Data (Definitions)

"Data elements that represent the lowest level of granularity. Depending on the context, this term may refer all the way back to the transactions from the operational systems, or it may refer to the base granularity held in a data warehouse." (Microsoft Corporation, "Microsoft SQL Server 7.0 Data Warehouse Training Kit", 2000)

"The most detailed granular data captured by a business process. Atomic data must be made available in the data presentation area to respond to unpredictable ad hoc queries." (Ralph Kimball & Margy Ross, "The Data Warehouse Toolkit 2nd Ed ", 2002)

"Data elements that represent the lowest level of detail. For example, in a daily sales report, the individual items sold would be atomic data, and roll-ups such as invoice and summary totals from invoices are aggregate data." (Sharon Allen & Evan Terry, "Beginning Relational Data Modeling 2nd Ed.", 2005)

"Data with the lowest level of granularity. Atomic-level data sits in a data warehouse and is time-variant (that is, accurate as of some moment in time now passed)." (William H Inmon, "Building the Data Warehouse", 2005)

"1.Data at the lowest chosen level of detail (granularity). The level of detail chosen depends on the information requirements of the enterprise. For example, address could be one atomic item, or address could be split into further composite items such as house identifier and city. Opposite of aggregate data. 2.Non-aggregated observations, or measurements of characteristics of individual units, which cannot be further decomposed and retain any useful meaning." (DAMA International, "The DAMA Dictionary of Data Management", 2011)

"Data at the lowest available level of detail or granularity." (Craig S Mullins, "Database Administration", 2012)

🛢DBMS: Column (Definitions)

"The logical equivalent of a field. A column contains an individual data item within a row or record." (Karen Paulsell et al, "Sybase SQL Server: Performance and Tuning Guide", 1996)

"In a SQL database table, the area, sometimes called a field, in each row that stores the data about an attribute of the object modeled by the table (for example, the ContactName column in the Customers table of the Northwind database). Individual columns are characterized by their maximum length and the type of data that can be placed in them. A column contains an individual data item within a row." (Microsoft Corporation, "SQL Server 7.0 System Administration Training Kit", 1999)

"A named portion of a table that can hold some number of data values of a particular datatype. Columns usually have some maximum width or number of bytes. The names and datatypes of a table's columns typically do not vary over time." (Bill Pribyl & Steven Feuerstein, "Learning Oracle PL/SQL", 2001)

"The area in each row that stores the data value for some attribute of the object modeled by the table." (Anthony Sequeira & Brian Alderman, "The SQL Server 2000 Book", 2003)

"The component of a database table that contains all of the data of the same name and type across all rows." (Bob Bryla, "Oracle Database Foundations", 2004)

"A piece of data that may be recorded for each row in a table. The corresponding formal database term is attribute." (Rod Stephens, "Beginning Database Design Solutions", 2008)

"Stored within tables, a column contains a particular piece of information." (Robert D Schneider & Darril Gibson, "Microsoft SQL Server 2008 All-in-One Desk Reference For Dummies", 2008)

"In a table, the area in each row that stores the data value for some attribute of the object presented in the table. For example, in an Employee table, a FirstName column would contain the first name of an employee." (Jim Joseph, "Microsoft SQL Server 2008 Reporting Services Unleashed", 2009)

"A data attribute as implemented in a relational database as a vertical component of a table, similar to a field in a flat file record." (Craig S Mullins, "Database Administration", 2012)

"The area in each row of a database table that stores the data value for some attribute of the object modeled by the table." (Microsoft, "SQL Server 2012 Glossary", 2012)

"A column is the data structure for storing a single value in a column family database." (Dan Sullivan, "NoSQL for Mere Mortals", 2015)

"The vertical component of a database table. A column has a name and a particular data type (for example, character, decimal, or integer)." (Sybase, "Open Server Server-Library/C Reference Manual", 2019)