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Q. Describe how an ER schema can be represented by relation schemas and constraints arising from ER design can be mapped to constraints on a relation schema.
The entity relationship data model is based on a perception of a real world that consists of basic objects called entities and of relationships among these objects. An entity is thing or object in the real world that is distinguishable from other objects. For eg., each person is an entity and band accounts can be considered as entities. Entities are described in a database by set of attributes. For eg., the attributes account number and balance may describe one particular acconunt in a bank and they form attributes of the account entity set. An extra attribute customer id is used to uniquely identify customers. A relationship is an association among several entities. For eg., a depositor relationship associates a customer with each account that he has. The set of all entities of the same type and the set of all relationship of the same type are called entity set and relationship set respectively. The overall logical structure of a database can be expressed graphically by and ER diagram, which is buily up using : R ectangles - which represent entity sets Ellipses - which represent attributes Diamonds - which represent relationships Lines - which represent link attributes to entity sets. Each component is labelled with the entity or relationship that it represents. Constraints to which the contents of database must confirm. For eg., mapping cardinalities, which express the number of entities to which another entity can be asociated via a relationship set.
Sequential File Organisation The most necessary way to organise the collection of records in a file is to use sequential Organisation. Records of the file are stored in series
Example -Find the employee name, salary, department number and average salary of his/her department, for those employees whose salary is more than the average salary of that depart
Q.1 Briefly discuss the different layers of ANSI SPARC architecture. Ans: The three layers of ANSI SPARC architecture are like this: 1. Internal view is at the lowest leve
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Define deadlock prevention. Deadlock prevention is a set of methods for ensuring that at least one of the four essential conditions like mutual exclusion, hold and wait, no pre
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Discuss how the one-to-one associations have to be implemented. Some of properties of associations can be implemented directly by providing suitable declarations of the data me
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Our company hires independent contractors to install equipment at precise locations across North America. We want to track the installation data and generate reports. The compan
This assignment is worth 45% of your final grade for this module. Marks will be awarded as follows: Prototypes (wireframe and web based prototype) You are expected
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