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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:
Describe disk manager and their work? Disk Manager: Responsible for fetching data regulated through file Manager from disk storage within Main memory and deciding what data to
Horizontal Fragmentation- Horizontal fragmentation groups together the tuples in a relation that are collectively used by the main transactions. A horizontal fragment is produced b
WOUND-WAIT
Question (a) Concurrent access to data from a database is a normal part of application program usage. Describe three approaches to concurrency control (b) Distinguish among
Example- Search the salary of employees who are not 'ANALYST' but get a salary below than or equal to any people employed as 'ANALYST'. SELECT EMPNO, ENAME, JOB, SAL FROMEMP
Example - ALTER TABLE emp MODIFY (empno NUMBER (7));
What is the most significant feature that does not directly map into programming language structures? Why? Association, since there are complex types of association, like as qu
Implementation of association as an object Implement as a separate association object, independent of either class, as in Figure. An association object is a group of pairs
what do you understand by enhanced entity-relationship
Why Like predicate used for? LIKE predicate: The LIKE predicate searches for strings in which have a certain pattern.
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