Logical Database Design.

Creating a database crystalline tendency is one of the first all-important(prenominal) go in designing a database. There ar quatern logical database beats that john be used hierarchical, network, congenatoral, or object-oriented. 1.Hierarchical: The first important logical database fabric. Still found in many mainframe-based, legacy systems. Records be arranged in a top-down parent/child structure. Each child potty be related to unless one parent 2.Network Developed to overtake the restrain scope of the hierarchical model. Similar to the hierarchical model only theres no parent/child distinction. Any prove shell may be associated with any number of diametrical record roles. 3.Relational Data are represented in the mastermind of put overs with rows and columns. Attributes are listed in columns, entity instances are represented by a row entry. 4.Object-Oriented Data attributes and trading operations on the attributes are encapsulated within objects. Obje cts tar sign inherit properties, can be generalized to take a shit new objects, and are reusable. The O-O model is a fairly new way of looking at things. For this story we will be using the relational model. With that decided, we can crop up on the collar steps in logical design: 1.Construct an E-R diagram to a set of relations (two-dimensional tables) 2.Represent apiece entity type as a relation. 3.Represent each relationship via native and external keys. This can be done by quest a couple of painless rules: ·Normalize the relations to promise a well-conditioned model ·Merge the relations to eliminate redundancies First introduced in 1970 by E. F. Codd the relational database model represents data in the form of tables (or relations). mathematically based yet relatively straightforward and easy to understand. Consists of three components: 1.Data Structure (via tables) 2.Data Manipulation (via SQL, for example) 3.Data Integrity (via formal task rules) Relations A relation is a named, two-dimensional table ! of data. The columns of the relation represent... If you want to get a full essay, drift it on our website: OrderEssay.net

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