GlossaryGuide

The process of duplicating a portion of a database from one environment to another and keeping the data in other environments consistent with the data in the source database.

A request for information from a database. There are three general methods for posing queries: (1) Choosing parameters from a menu: In this method, the database system presents a list of parameters from which to choose. This is perhaps the easiest way to pose a query because the menus provide guidance, but it is also… Continue reading Database Query

Defines a data object as containing code (sequences of computer instructions) and data (information that the instructions operate on). Traditionally, code and data have been kept apart. In an object-oriented data model, the code and data are merged into a single indivisible thing—an object.

Data items organized as a set of formally described tables from which data can be accessed or reassembled in many ways without having to reorganize the database tables. Each table (sometimes called a relation) contains one or more data categories in columns. Each row contains a unique instance of data for the categories defined by… Continue reading Relational Model

A special case of the hierarchical data model in which each record type can have multiple owners (e.g., purchase orders are owned by both customers and products).

A data model that links records together like a family tree, but each record type has only one owner (e.g., a purchase order is owned by only one customer). Hierarchical data structures were widely used in the first mainframe database management systems. However, due to their restrictions, they often cannot be used to relate structures… Continue reading Hierarchical Model

A file structure involving data records that have no structured interrelationship. A flat file takes up less computer space than a structured file but requires the database application to know how the data are organized within the file.

The structure or format of a database, described in a formal language supported by the database management system. Schemas are generally stored in a data dictionary. Although a schema is defined in text database language, the term is often used to refer to a graphical depiction of the database structure. The following database models are… Continue reading Database Model/Schema

A collection of programs that enables information to be stored in, modified, and extracted from a database. There are many different types of DBMSs, ranging from small systems that run on personal computers to huge systems that run on mainframes. From a technical standpoint, the systems can differ widely. The terms relational, network, flat, and… Continue reading Database Management System/Software (DBMS)

A file that defines the basic organization of a database. A database dictionary contains a list of all files in the database, the number of records in each file, and the names and types of each data field. Most database management systems keep the data dictionary hidden from users to prevent them from accidentally destroying… Continue reading Database Dictionary