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ActiveX Data Objects (ADO) - Microsoft's high-level interface for data objects. ADO was designed to eventually replace Data Access Objects (DAO) and Remote Data Objects (RDO). Unlike RDO and DAO, which are designed only for accessing relational databases, ADO is more general and can be used to access all sorts of different types of data, including web pages, spreadsheets, and other types of documents. Together with OLE DB and ODBC, ADO is one of the main components of Microsoft's Universal Data Access (UDA) specification, which is designed to provide a consistent way of accessing data regardless of how the data are structured.
Alternate key - A candidate key that was not chosen to be the primary key.
Attribute - A property of an entity.
Candidate key - A minimal collection of columns (attributes) in a table on which all columns are functionally dependent but that has not necessarily been chosen as the primary key.
Catalog - A source of information on the types of entities, attributes, and relationships in a database.
Data archive - A place where historical data are kept. Data that are no longer needed in the database but must be retained for future reference are removed from the database and placed in the archive.
Data definition language - A language that is used to communicate the structure of a database to the database management system.
Data dictionary - A tool used to store descriptions of the entities, attributes, relationships, programs, and so on that are associated with an organization's database.
Data Source Name (DSN) - DSN provides connectivity to a database through an ODBC driver. The DSN contains database name, directory, database driver, UserID, password, and other information. Once you create a DSN for a particular database, you can use the DSN in an application to call information from the database. DSN is often used by Active Server Pages (ASP) and Visual Basic programs when a query to a database is necessary to retrieve information.
Data warehouse - A subject-oriented, integrated, time-variant, nonvolatile collection of data in support of management's decision-making process.
Database - A structure that can store information about various types of entities and about the relationships among the entities.
Database Administration (DBA) - The individual or group that is reponsible for the database.
Database design - The process of determining the content and arrangement of data in a database in order to support some activity on behalf of a user or group of users.
Database Design Language (DBDL) - A relational-like language that is used to represent the result of the database design process.
Database Management System (DBMS) - A software package that is designed to manipulate the data in a database on behalf of a user.
Deletion anomaly - A deletion anomaly occurs when you delete data from a relation and unintentionally lose other critical data. This problem can occur as a result of a faulty database design.
Distributed database - A database that is stored on computers at several sites of a computer network and from which users can access data at any site on the network.
Domain - (1) A group of computers and devices on a network that are administered as a unit with common rules and procedures. Within the Internet, domains are defined by the IP address. All devices sharing a common part of the IP address are said to be in the same domain. (2) In database technology, domain refers to the description of an attribute's allowed values. The physical description is a set of values the attribute can have, and the semantic, or logical, description is the meaning of the attribute.
Entity - An object (person, place, or thing) of interest.
Entity integrity - The rule that no column (attribute) that is part of the primary key may accept null values.
Entity-Relationship (E-R) diagram - A graphic model for database design in which entities are represented as rectangles and relationships are represented as either arrows or diamonds connected to the entities they relate.
Field - The smallest unit of data to which a name can be assigned; it can be thought of as a column in a table.
File - A collection of bytes (characters) on a disk; a file could be data, a program, a document created with a word processor, etc. Often refers to a data file, which is a structure used to store data about some entity. Such a file can be thought of as a table. The rows in such a table are called records, and the columns are called fields.
Flat-file database - A relatively simple database system in which each database is contained in a single table. In contrast, relational database systems can use multiple tables to store information, and each table can have a different record format.
Foreign key - A column (attribute) or collection of columns in a table whose value is required either to match the value of a primary key in another table or to be null.
Form - A screen object used to maintain, view, and print records from a database.
Functionally dependent - Column B is functionally dependent on column A (or on a collection of columns) if a value for A determines a single value for B at any one time.
Grouping - Creating collections of records that share some common characteristic.
Identifying relationship - A relationship that is necessary for identification of an entity.
Independent entity - An entity that does not require a relationship to another entity for identification.
Index - A file that relates key values to records that contain those key values.
Information-level design - The step during database design in which the goal is to create a clean, DBMS-independent design that will support user requirements.
Inheritance - The property that states that a subclass inherits the structure of the class as well as the methods.
Insertion anomaly - An insertion anomaly occurs when you cannot add a row to a relation because you do not know the entire primary key value. Entity integrity prevents you from leaving any part of a primary key null. This problem can occur as a result of a faulty database design.
Java Database Connectivity (JDBC) - A Java application program interface (API) that enables Java programs to execute SQL statements. This allows Java programs to interact with any SQL-compliant database. Since nearly all relational DBMSs support SQL, and because Java itself runs on most platforms, JDBC makes it possible to write a single database application that can run on different platforms and interact with different DBMSs. JDBC is similar to ODBC but is designed specifically for Java programs, whereas ODBC is language-independent.
Join - In the relational algebra, the operation in which two tables are connected on the basis of common data
Journal - A record of all changes in the database; also called a log. Used to recover a database that has been damaged or destroyed.
Key - A field that is used for sorting. Key types are primary, foreign, candidate, alternate, and secondary.
Lock - A device that prevents other users from accessing a portion of a database.
Many-to-many relationship - A relationship between two entities in which each occurrence of each entity is related to many occurrences of the other entity.
Method - An action defined for an object (class).
Nonkey attribute - An attribute (column) that is not part of the primary key.
Normalization - The process of removing repeating groups to produce a first normal form table. Sometimes refers to the process of creating a third normal form table.
Null - A data value meaning "empty" or "unknown" or "not applicable." The absence of a value.
Object - A unit of data and the actions that can take place on those data.
Object Linking and Embedding (OLE) - A compound document standard developed by Microsoft. It enables you to create objects with one application and then link or embed them in a second application. Embedded objects retain their original format and links to the application that created them. Support for OLE is built into the Windows and Macintosh operating systems.
Object-Oriented Database Management System (OODBMS) - A DBMS in which data and the methods that operate on those data are encapsulated into objects.
One-to-many relationship - A relationship between two entities in which each occurrence of the first entity is related to many occurrences of the second entity, but each occurrence of the second entity is related to only one occurrence of the first entity.
One-to-one relationship - A relationship between two entities in which each occurrence of the first entity is related to one occurrence of the second entity and each eccurrence of the second entity is related to one occurrence of the first entity.
Open DataBase Connectivity (ODBC) - A standard database access method developed by Microsoft Corporation. The goal of ODBC is to make it possible to access any data from any application, regardless of which DBMS is handling the data. ODBC manages this by inserting a middle layer, called a database driver, between an application and the DBMS. The purpose of this layer is to translate the application's data queries into commands that the DBMS understands. For this to work, both the application and the DBMS must be ODBC-compliant. That is, the application must be capable of issuing ODBC commands and the DBMS must be capable of responding to them.
Physical-level design - The step during database design in which a design for a given DBMS is produced from the final information-level design.
Primary key - A minimal collection of columns (attributes) in a table on which all columns are functionally dependent and that is chosen as the main direct-access vehicle to individual rows.
Query - A question, the answer to which is found in the database; also used to refer to a command in a nonprocedural language such as SQL that is used to obtain the answer to such a question.
Query-By-Example (QBE) - A data manipulation language for relational databases in which users indicate the action to be taken by filling in portions of blank tables on the screen.
Query language - A language that is designed to permit users to obtain information easily from the database.
Record - A collection of related fields; can be thought of as a row in a table.
Recovery - The process of restoring a database that has been damaged or destroyed.
Redundancy - Duplication of data.
Referential integrity - The rule that if a table A contains a foreign key that matches the primary key of table B, then the value of this foreign key must either match the value of the primary key for some row in table B or be null.
Relation - A two-dimensional table-style collection of data in which all entries are single-valued; each column has a distinct name; all the values in a column are values of the attribute that is identified by the column name, the order of columns is irrelevant; each row is distinct; and the order of rows is irrelevant.
Relational algebra - A relational data manipulation language in which new tables are created from existing tables through the use of a set of operations.
Relational database - A collection of relations (tables).
Relationship - An association between entities.
Repeating group - Several entries at a single location in a table.
Replication - Duplicating data at more than one site in a distributed database.
Schema - The structure of a database system, described in a formal language supported by the DBMS. In a relational database, the schema defines the tables, the fields in each table, and the relationships between fields and tables. Schemas are generally stored in a data dictionary.
Secondary key - A column (attribute) or collection of columns that is of interest for retrieval purposes (and that is not already designated as some other type of key).
Security - The protection of the database against unauthorized access.
Sort key - The field on which data are sorted.
Stored procedure - A file containing a collection of SQL statements that are available for future use.
Structure - One of the two components of a data model: the manner in which the system structures data or, at least, the manner in which the users perceive that the data are structured.
Structured Query Language (SQL) - A very popular relational data definition and manipulation language that is used in many relational DBMSs.
Switchboard - A form used to provide controlled access to the data, forms, reports, and other content of a database.
Synchronization - The periodic exchange by a DBMS of all updated data bwteen two databases in a replica set.
Table - In the datase environment, another name for a relation.
Trigger - An action that takes place qutomatically when an associated database operation occurs.
Tuple - A formal name for a row in a table.
Union - A combination of two tables consisting of all records that are in either table.
Union-compatible - Two tables are union-compatible if they have the same number of fields and if their corresponding fields have identical data types.
Update anomaly - An update anomaly occurs when you change one attribute value and either the DBMS must make more than one change to the database or else the database ends up containing inconsistent data. This problem can occur as a result of faulty design.
User view - The view of data that is necessary to support the operations of a particular user.
Utility services - DBMS-supplied functions that assist in the maintenance of the database.
View - An application program's or an individual user's picture of the database.
Wild card - A symbol that can be used in place of an unknown character or group of characters in a query.

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		ActiveX Data Objects (ADO) - Microsoft's high-level interface for data objects. ADO was designed to eventually replace Data Access Objects (DAO) and Remote Data Objects (RDO). Unlike RDO and DAO, which are designed only for accessing relational databases, ADO is more general and can be used to access all sorts of different types of data, including web pages, spreadsheets, and other types of documents. Together with OLE DB and ODBC, ADO is one of the main components of Microsoft's Universal Data Access (UDA) specification, which is designed to provide a consistent way of accessing data regardless of how the data are structured. Alternate key - A candidate key that was not chosen to be the primary key. Attribute - A property of an entity. Candidate key - A minimal collection of columns (attributes) in a table on which all columns are functionally dependent but that has not necessarily been chosen as the primary key. Catalog - A source of information on the types of entities, attributes, and relationships in a database. Data archive - A place where historical data are kept. Data that are no longer needed in the database but must be retained for future reference are removed from the database and placed in the archive. Data definition language - A language that is used to communicate the structure of a database to the database management system. Data dictionary - A tool used to store descriptions of the entities, attributes, relationships, programs, and so on that are associated with an organization's database. Data Source Name (DSN) - DSN provides connectivity to a database through an ODBC driver. The DSN contains database name, directory, database driver, UserID, password, and other information. Once you create a DSN for a particular database, you can use the DSN in an application to call information from the database. DSN is often used by Active Server Pages (ASP) and Visual Basic programs when a query to a database is necessary to retrieve information. Data warehouse - A subject-oriented, integrated, time-variant, nonvolatile collection of data in support of management's decision-making process. Database - A structure that can store information about various types of entities and about the relationships among the entities. Database Administration (DBA) - The individual or group that is reponsible for the database. Database design - The process of determining the content and arrangement of data in a database in order to support some activity on behalf of a user or group of users. Database Design Language (DBDL) - A relational-like language that is used to represent the result of the database design process. Database Management System (DBMS) - A software package that is designed to manipulate the data in a database on behalf of a user. Deletion anomaly - A deletion anomaly occurs when you delete data from a relation and unintentionally lose other critical data. This problem can occur as a result of a faulty database design. Distributed database - A database that is stored on computers at several sites of a computer network and from which users can access data at any site on the network. Domain - (1) A group of computers and devices on a network that are administered as a unit with common rules and procedures. Within the Internet, domains are defined by the IP address. All devices sharing a common part of the IP address are said to be in the same domain. (2) In database technology, domain refers to the description of an attribute's allowed values. The physical description is a set of values the attribute can have, and the semantic, or logical, description is the meaning of the attribute. Entity - An object (person, place, or thing) of interest. Entity integrity - The rule that no column (attribute) that is part of the primary key may accept null values. Entity-Relationship (E-R) diagram - A graphic model for database design in which entities are represented as rectangles and relationships are represented as either arrows or diamonds connected to the entities they relate. Field - The smallest unit of data to which a name can be assigned; it can be thought of as a column in a table. File - A collection of bytes (characters) on a disk; a file could be data, a program, a document created with a word processor, etc. Often refers to a data file, which is a structure used to store data about some entity. Such a file can be thought of as a table. The rows in such a table are called records, and the columns are called fields. Flat-file database - A relatively simple database system in which each database is contained in a single table. In contrast, relational database systems can use multiple tables to store information, and each table can have a different record format. Foreign key - A column (attribute) or collection of columns in a table whose value is required either to match the value of a primary key in another table or to be null. Form - A screen object used to maintain, view, and print records from a database. Functionally dependent - Column B is functionally dependent on column A (or on a collection of columns) if a value for A determines a single value for B at any one time. Grouping - Creating collections of records that share some common characteristic. Identifying relationship - A relationship that is necessary for identification of an entity. Independent entity - An entity that does not require a relationship to another entity for identification. Index - A file that relates key values to records that contain those key values. Information-level design - The step during database design in which the goal is to create a clean, DBMS-independent design that will support user requirements. Inheritance - The property that states that a subclass inherits the structure of the class as well as the methods. Insertion anomaly - An insertion anomaly occurs when you cannot add a row to a relation because you do not know the entire primary key value. Entity integrity prevents you from leaving any part of a primary key null. This problem can occur as a result of a faulty database design. Java Database Connectivity (JDBC) - A Java application program interface (API) that enables Java programs to execute SQL statements. This allows Java programs to interact with any SQL-compliant database. Since nearly all relational DBMSs support SQL, and because Java itself runs on most platforms, JDBC makes it possible to write a single database application that can run on different platforms and interact with different DBMSs. JDBC is similar to ODBC but is designed specifically for Java programs, whereas ODBC is language-independent. Join - In the relational algebra, the operation in which two tables are connected on the basis of common data Journal - A record of all changes in the database; also called a log. Used to recover a database that has been damaged or destroyed. Key - A field that is used for sorting. Key types are primary, foreign, candidate, alternate, and secondary. Lock - A device that prevents other users from accessing a portion of a database. Many-to-many relationship - A relationship between two entities in which each occurrence of each entity is related to many occurrences of the other entity. Method - An action defined for an object (class). Nonkey attribute - An attribute (column) that is not part of the primary key. Normalization - The process of removing repeating groups to produce a first normal form table. Sometimes refers to the process of creating a third normal form table. Null - A data value meaning "empty" or "unknown" or "not applicable." The absence of a value. Object - A unit of data and the actions that can take place on those data. Object Linking and Embedding (OLE) - A compound document standard developed by Microsoft. It enables you to create objects with one application and then link or embed them in a second application. Embedded objects retain their original format and links to the application that created them. Support for OLE is built into the Windows and Macintosh operating systems. Object-Oriented Database Management System (OODBMS) - A DBMS in which data and the methods that operate on those data are encapsulated into objects. One-to-many relationship - A relationship between two entities in which each occurrence of the first entity is related to many occurrences of the second entity, but each occurrence of the second entity is related to only one occurrence of the first entity. One-to-one relationship - A relationship between two entities in which each occurrence of the first entity is related to one occurrence of the second entity and each eccurrence of the second entity is related to one occurrence of the first entity. Open DataBase Connectivity (ODBC) - A standard database access method developed by Microsoft Corporation. The goal of ODBC is to make it possible to access any data from any application, regardless of which DBMS is handling the data. ODBC manages this by inserting a middle layer, called a database driver, between an application and the DBMS. The purpose of this layer is to translate the application's data queries into commands that the DBMS understands. For this to work, both the application and the DBMS must be ODBC-compliant. That is, the application must be capable of issuing ODBC commands and the DBMS must be capable of responding to them. Physical-level design - The step during database design in which a design for a given DBMS is produced from the final information-level design. Primary key - A minimal collection of columns (attributes) in a table on which all columns are functionally dependent and that is chosen as the main direct-access vehicle to individual rows. Query - A question, the answer to which is found in the database; also used to refer to a command in a nonprocedural language such as SQL that is used to obtain the answer to such a question. Query-By-Example (QBE) - A data manipulation language for relational databases in which users indicate the action to be taken by filling in portions of blank tables on the screen. Query language - A language that is designed to permit users to obtain information easily from the database. Record - A collection of related fields; can be thought of as a row in a table. Recovery - The process of restoring a database that has been damaged or destroyed. Redundancy - Duplication of data. Referential integrity - The rule that if a table A contains a foreign key that matches the primary key of table B, then the value of this foreign key must either match the value of the primary key for some row in table B or be null. Relation - A two-dimensional table-style collection of data in which all entries are single-valued; each column has a distinct name; all the values in a column are values of the attribute that is identified by the column name, the order of columns is irrelevant; each row is distinct; and the order of rows is irrelevant. Relational algebra - A relational data manipulation language in which new tables are created from existing tables through the use of a set of operations. Relational database - A collection of relations (tables). Relationship - An association between entities. Repeating group - Several entries at a single location in a table. Replication - Duplicating data at more than one site in a distributed database. Schema - The structure of a database system, described in a formal language supported by the DBMS. In a relational database, the schema defines the tables, the fields in each table, and the relationships between fields and tables. Schemas are generally stored in a data dictionary. Secondary key - A column (attribute) or collection of columns that is of interest for retrieval purposes (and that is not already designated as some other type of key). Security - The protection of the database against unauthorized access. Sort key - The field on which data are sorted. Stored procedure - A file containing a collection of SQL statements that are available for future use. Structure - One of the two components of a data model: the manner in which the system structures data or, at least, the manner in which the users perceive that the data are structured. Structured Query Language (SQL) - A very popular relational data definition and manipulation language that is used in many relational DBMSs. Switchboard - A form used to provide controlled access to the data, forms, reports, and other content of a database. Synchronization - The periodic exchange by a DBMS of all updated data bwteen two databases in a replica set. Table - In the datase environment, another name for a relation. Trigger - An action that takes place qutomatically when an associated database operation occurs. Tuple - A formal name for a row in a table. Union - A combination of two tables consisting of all records that are in either table. Union-compatible - Two tables are union-compatible if they have the same number of fields and if their corresponding fields have identical data types. Update anomaly - An update anomaly occurs when you change one attribute value and either the DBMS must make more than one change to the database or else the database ends up containing inconsistent data. This problem can occur as a result of faulty design. User view - The view of data that is necessary to support the operations of a particular user. Utility services - DBMS-supplied functions that assist in the maintenance of the database. View - An application program's or an individual user's picture of the database. Wild card - A symbol that can be used in place of an unknown character or group of characters in a query.