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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.
) Define a job scheduling strategy that will meet business requirement of reporting availability by 6am CST for the following cubes? Show the job scheduling dependencies in a picto
Explain the structure of well formed formulae in relational calculus. Ans: a. An atom is a formula b. If P1 is a formula, after that so are ¬P1 and (P1) c. If P1 and P2 a
what is file organization? what are file organization techniques.explain in detail? explain random file organization technique, multikey file organization technique?what is indexin
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Which operation is used if we are interested in only certain columns of a table? PROJECTION operation is used if we are interested in only certain columns of a table.
Consider the following relational schema: Doctor(DName,Reg_no) Patient(Pname, Disease) Assigned_To (Pname,Dname) Give expression in both Tuple calculus and Domain calculus for
Recovery Techniques: After Reading the types of failures and database errors, let us talk about how to recover from the failures. Recovery can be complete using/restoring the previ
Define the terms i) DDL ii) DML DDL: Data base schema is specified by a set of definitions expressed by a special language known as a data def
A buyer for a large department store chain must place orders with an athletic shoe manufacturer six months prior to the time the shoes will be sold in the department stores. In par
How to Insert data in your table from another table? insert into e.g, To insert tuples from employee into N_emp created above, use following statement Insert into N_emp
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