Beginning Database Design- P23

Beginning Database Design- P23:This book focuses on the relational database model from a beginning perspective. The title is, therefore,Beginning Database Design. A database is a repository for data. In other words, you can store lots of informationin a database. A relational database is a special type of database using structures called tables.Tables are linked together using what are called relationships. You can build tables with relationshipsbetween those tables, not only to organize your data, but also to allow later retrieval of information fromthe database....
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Beginning Database Design- P23 GlossaryMaterialized view — A physically preconstructed view of data containing data copied into the material-ized view. Materialized views can be highly efficient in read-only environments and are often used forreplication, distribution and in data warehouses.Metadata — The tables and the fields defining the structure of the data; the data about the data.Method — The equivalent to a relational database stored procedure, except that it executes on the datacontents of an object, within the bounds of that object.Microsoft Windows — The Microsoft Windows operating system.Multi-valued dependency — A field containing a comma-delimited list or collection of some kind. A col-lection could be an array of values of the same type. Those multiple values are dependent as a whole onthe primary key, the whole meaning the entire collection in the comma-delimited list. Each individualvalue is not dependent on the primary key.Nested query — A query executed from within another query. In theory, queries can be nested up to anynumber of hierarchical layers. The only limitation is on complexity and the abilities of the programmer.Network — A system of connected computers. A local area network (LAN) is contained within a singlecompany, in a single office. A wide area network (WAN) is generally distributed across a geographicalarea — even globally. The Internet is a very loosely connected network, meaning that it is usable by any-one and everyone.Network database model — Essentially a refinement of the hierarchical database model. The networkmodel allows child tables to have more than one parent, thus creating a networked-like table structure.Multiple parent tables for each child allow for many-to-many relationships, in addition to one-to-manyrelationships.Non trivial multi-valued dependency — A multi-valued dependency with more than two fields in thetable. (See Multi valued dependency.)Non-identifying relationship — The child table is not dependent on the parent table, such that the childtable includes the parent table primary key as a foreign key, but not as part of the child table’s primarykey. In other words, the parent record does not require, that a related record, exists in the child table. Aforeign key field can contain a NULL value, and it can’t be a part of the primary key because a primarykey requires uniqueness.Normal Forms — The steps contained within the process of Normalization. Normal Forms are cumulative,such that a database model in 3rd Normal Form is in both 2nd and 1st Normal Forms, but not Boyce-Codd(can be the same as 3rd Normal Form), 4th, 5th Normal Form, or Domain Key Normal Form.Normalization — The process of simplifying the structure of data. Normalization increases granularityand Granularity is the scope of a definition for any particular thing. The more granular a data model is,the easier it becomes to manage, up to a point, depending, of course, on the application of the databasemodel.NOT NULL constraint — A constraint that implies a field must have a value placed into it; otherwise, anerror is returned. 413Glossary NULL — A field that has never been initialized with any value. A NULL field setting allows a field to con- tain nothing when a record is created or changed in a table. Number — A numeric datatype allowing only numbers of various formats. Number crunching — Computer jargon for large quantities of extremely complex calculations. Object — In object methodology, the creation (instantiation) of a class at run-time, such that multiple object instances can be created from a class. An object is also a generic term applied to anything tangible, such as a table in a relational database. Object database model — A model that provides a three-dimensional structure to data where any item in a database can be retrieved from any point very rapidly. Whereas the relational database model lends itself to retrieval of groups of records in two dimensions, the object database model is very efficient for finding unique items. Consequently, the object database model performs very poorly when retrieving more than a single item, at which the relational database model is very good. Object-relational database model — The object-relational database model includes minimal aspects of the object database model into the relational database model. In some respects, the object-relational database model was created in answer to conflicting capabilities of relational and object database models — and also as a commercial competitor to the object database model. The object database model is somewhat spherical in nature, allowing access to unique elements anywhere within a database structure, with extremely high performance. The object database model performs extremely poorly when retrieving more than a single data item. The relational database model, on the other hand, contains records of data in tables across two dimensions. The relational database model is best suited for retrieval of groups of data but can also be used to access unique data items fairly efficiently. OLAP — See Online Analytical Processing. OLTP — See Online Transaction Processing. ON clause — The ON clause is an ANSI standard join format that allows exact field join specifications when you want to include one or more fields in a join, which have different names in different tables. One-to-many relationship — The relationship between two tables dictated by having one record in one table, and many related records in another table. One-to-one relationship — The relationship between two tables dictated by having one record in each table, and not more than one ...