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Explain the concepts of relational data model?
Relational Data Model - The relational model was first introduced through Prof. E.F. Codd of the IBM Research in the year 1970 and attracted immediate attention because of its simplicity and mathematical foundation. The model uses the concept of a mathematical relation (such as a table of values) as its primary building block, and has its theoretical basis within set theory and first-order predicate logic. The relational model represents the database as a collection of relations. The relational model such as all other models consists of three basic elements:
Differentiate between Key and superkey? Key and superkey - A key a single attribute or a combination of two or more attributes of an entity set in which is used to identify o
State The position of object at any moment is called state. An object can have many states depend upon time. After receiving some input instructions, the object can change its
What is B-Tree? A B-tree eliminates the redundant storage of search-key values .It permits search key values to appear only once.
Concatenation operator Example : Printing name and job as one string as column name employees: SELECT ENAME||JOB "EMPLOYEES" FROM EMP;
Illustrate the Deployment Diagram A deployment diagram shows all nodes on network, their processor execution and interconnections. In a dynamic model, this is used to represen
Define Query by Example QBE is a query language relies upon domain calculus and has two dimensional syntax. The queries are written in the horizontal and vertical dimensions of
Removing a Synonym: DROP SYNONYM D30;
What are the two types of blocks in the fixed -length representation? Define them. Anchor block: Have the first record of a chain. Overflow block: Have the records other tha
I need a help with my assignment of data envelopment analysis which is due for submission next week on monday the 10th Dec. Will you be able to help so that I can submit it on tim
Compare wait-die deadlock prevention scheme with wait-wound scheme Ans: Wait-Die Scheme a) Based upon a nonpreemptive technique. b) If Pi requests a resource present
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