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| Database Management System (DBMS) |
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Definition
| The specialized computer program that manages and controls the data and interfaces between the data and the application programs. |
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| The combination of the database, the database management system, and the application programs that access the database through the database management system. |
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| The person reasponsible for coodinating, controlling, and managing the data in the database. |
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| Very large databases that contain both detailed and summarized data for a number of years and that are used for analysis rather than transaction processing. |
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| Accessing information stored in a data warehouse through statistical analysis or artifical intelligence techniques to "discover" unhypothesized relationships in the data. |
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| A document that illustrates the arrangement of items of data in input, output, and file records. |
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| The manner in which a user or programmer conceptually organizes, views, and understands the relationships among data items. Contrast with physical view. |
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| The way data are physically arranged and stored in the computer system. Contrast with logical view. |
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| A description of the types of data elements that are in the database, the relationships among the data elements, and the structure or overall logical model used to organize and describe the data. |
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| The organization-wide view of the entire database. It lists all data elements in the database and the relationships between them. Contrast with external-level schema and internal-level schema. |
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| An individual user's or application program's view of a subset of the organization's database. Each of the individual user views is also referred to as a subschema. |
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| (1) A subset of the schema that includes only those data items used in a particular application program or by a particular user. (2) The way the user defines the data and the data relationships. |
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| A low-level view of the entire database describing how the data are actually stored and accessed. It includes information about record layouts, definitions, addresses, indexes, and so forth. |
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| An ordered collection of data elements that contain information about the structure of the database. For each data element stored in the database, such as the customer number, there is a corresponding record in the data dictionary describing it. |
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Term
| Data Definition Language (DDL) |
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Definition
| A database management system language that ties the logical and physical views of the data together. It is used to build the data dictionary, initialize or create the database, describe the logical views for each individual user or programmer, and specify any limitations or constraints on security imposed on database records or fields. |
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| Data Manipulation Language (DML) |
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Definition
| A database management system language used for data maintenance, which includes such operations as updating, inserting, and deleting portions of the database. |
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Term
| Data Querry Langauge (DQL) |
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Definition
| A high-level, English-like command language that is used to interrogate a database. The DQL retrives, sorts, orders, and presents subsets of the database in response to user queries. |
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| A language that simplifies report creation. Typically, user need only specify which data elements they want printed and how the report should be formatted. The report writer searches the database, extracts the specified data items, and prints them according to the user-specified format. |
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| An abstract representation of the contents of a database. |
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| A database model in which all data elements are logically viewed as being stored in the form of two dimensional tables called "relations." In these tables each row represents a unique entity or record. Each column represents a field where the record's attributes are stored. The tables serve as the building blocks from which data relationships can be created. |
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| The tables used to store data in a relational database. |
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| A row in a relation. A tuple contains data about a specific accurrence in a database table. For example, each row in the inventory table contains all the pertinent data about a particular inventory item. |
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Definition
| The attribute, or combination of attributes, that uniquely identifies a specific row in a database table. The primary key is used to distinguish, order, and reference recods in a database. |
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| An attribute appearing in one table that is itself the primary key of another table. Foreign keys are used to link tables. |
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| Consequently, if the value of that data item is not changed in every row in which it is stored, inconsistencies in the database will result. |
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| The problem arises because new information about new attributes cannot be entered in the database without violating integrity rules. |
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| Deleting a row from that table may result in the loss of all information about those attributes that are not characteristics of the primary key. |
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| A database managemnt system that uses the relational data model developed by Dr. E.F. Codd in 1970. |
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| A design constraint in a relational database, requiring that the primary key have a non-null value. This ensures that a specific object exists in the world and can be identified by reference to its primary key value. |
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| Referential Integrity Rule |
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| This constraint ensures consistency in the database. |
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| The process of following the guidelines for properly designing a relational database that is free from delete, insert, and update anomalies. |
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