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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.
Draw an ER diagram that represents the information described below. Show all entity sets, relationship sets, primary keys, and the mapping cardinality of the relationship sets.
Which is a valid SQL type? A valid SQL Should be in CHARACTER it is should be NUMERIC and FLOAT.
Most computer systems authenticate users by asking them for the user name and password. However, the user names and passwords often can be guessed by hackers. Suggest an automated,
Define instance and schema? Instance: Collection of data kept in the data base at a particular moment is known as an Instance of the database. Schema: The o
What is data definition language? Explain it in detail? The SQL DDL allows specification of not only a set of relations, but also information after each relation, containing
Design Documentation The Design Document shall be an extension of Requirements Analysis Design. "The Design Document will comprise a revised and much more detailed descrip
Question: (a) Discuss the difference between a composite key and a composite attribute. How would each be indicated in an E-R diagram? Support your answer with appropriate exam
A database named yourusernameFMA has been set up for you to use for this assignment. For the FMA you must create the required tables and run the queries using this database. If y
What is nested relational model? The nested relational model is an extension of relational model in which domains might be either atomic or relation valued.
List the internal controls that should be in effect solely because a EDP system is employed, classifing them as (1) Those controls pertaining to input of information and (2) All ot
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