Question 3 Assignment 2 Deadline Day 24/11/2018 23:59 485833

Pg 06question Threeassignment 2deadline Day 24112018 2359total

Pg 06question Threeassignment 2deadline Day 24112018 2359total

Consider the following relational database schema. Suppose that all the relations were created by (and hence are owned by) user X, who wants to grant the following privileges to user accounts A, B, C, and D: Employee (Fname, Minit, Lname, Ssn, Bdate, Address, Sex, Salary, Super_ssn, Dno), Department (Dname, Dnumber, Mgr_ssn, Mgr_start_date), Department_Locations (Dnumber, Dlocation), Project (Pname, Pnumber, Plocation, Dnum), Works_On (Essn, Pno, Hours), Dependents (Essn, Dependent_name, Sex, Bdate, Relationship).

Write SQL statements to grant privileges accordingly, using views where appropriate:

  • (a) Account A can modify DEPARTMENT and PROJECT relations: GRANT UPDATE ON DEPARTMENT, PROJECT TO A
  • (b) Account B can retrieve only DNAME, MGR_SSN, DNUMBER, and DLOCATION attributes of DEPARTMENT and DEPT_LOCATIONS: CREATE VIEW DEPARTMENT_INFO as SELECT DNAME, MGR_SSN, DNUMBER, DLOCATION FROM DEPARTMENT, DEPT_LOCATIONS WHERE DEPARTMENT.DNUMBER=DEPT_LOCATIONS.DNUMBER; then GRANT SELECT ON DEPARTMENT_INFO TO B
  • (c) Account C can insert or update on WORKS_ON relation and can grant these privileges to others: GRANT INSERT, UPDATE ON WORKS_ON TO C WITH GRANT OPTION
  • (d) Account D can retrieve any attribute of DEPENDENTS and WORKS_ON: GRANT SELECT ON DEPENDENTS, WORKS_ON TO D

Consider the Student_Course table with fields: Std_ID, Course_ID, Std_Course_Mark, and the Course table with fields: Course_ID, Course_Name, Maximum_Mark, Minimum_Mark. Write a trigger named ‘Max_Min’ that updates Maximum_Mark and Minimum_Mark in the Course table whenever a new row is inserted into Student_Course:

CREATE TRIGGER Max_Min ON Student_Course


FOR INSERT


AS


DECLARE @Course_ID INT


BEGIN


SELECT @Course_ID = C.Course_ID FROM INSERTED I JOIN Course C ON I.Course_ID = C.Course_ID


UPDATE Course


SET Maximum_Mark = (SELECT MAX(Std_Course_Mark) FROM Student_Course WHERE Course_ID = @Course_ID),


Minimum_Mark = (SELECT MIN(Std_Course_Mark) FROM Student_Course WHERE Course_ID = @Course_ID)


WHERE Course.COURSE_ID = @Course_ID


END

Paper For Above instruction

Distributed database systems are designed to manage data across multiple locations, providing advantages such as improved efficiency, increased parallelism, enhanced security, and better resource utilization. Fragmentation, a core concept within distributed databases, plays a significant role in optimizing data management and access. This essay explores the advantages of fragmentation, describes how it enhances system performance, and discusses its implications for distributed database architecture.

Advantages of Fragmentation in Distributed Database Management Systems

Fragmentation divides a database into smaller, manageable pieces called fragments, which are stored across different sites. This division can be horizontal, vertical, or derived, each serving specific organizational needs. One of the primary advantages of fragmentation is improved data accessibility and performance. By localizing data that is frequently accessed together, fragmentation reduces network traffic and latency, leading to faster query execution. For example, horizontal fragmentation based on the employee’s department allows queries related to a specific department to access only relevant tuples, reducing the amount of data processed and transmitted.

Another advantage is enhanced security. Sensitive data can be isolated in specific fragments, restricting access to authorized users only. Vertical fragmentation allows sensitive columns, such as salary or social security number, to be stored separately, thereby limiting exposure of critical information. Additionally, fragmentation enables better resource utilization by distributing data across multiple sites, allowing concurrent processing and load balancing. This parallelism increases system throughput and efficiency, minimizing bottlenecks and enabling scalable growth of the database system.

Furthermore, fragmentation facilitates easier maintenance and data consistency. Changes or updates to a particular fragment can be managed independently, simplifying administrative tasks. Derived fragmentation, which involves partitioning data based on foreign key relationships, maintains referential integrity across distributed fragments, which is crucial for ensuring data consistency within the system.

Vertical and Horizontal Fragmentation

Vertical fragmentation involves dividing a relation into subsets of columns, each containing the primary key and other relevant attributes. This approach is beneficial when different applications or user groups need specific subsets of attributes, reducing data redundancy and enhancing access efficiency. For example, a vertical fragment of the Employee relation might include only employee contact information and addresses, rather than the entire employee record.

Horizontal fragmentation, on the other hand, partitions data based on specific selection criteria, creating subsets of rows that satisfy certain conditions. For instance, employee data for department DNO=5 can be stored in a horizontal fragment, enabling efficient retrieval of data pertinent to that department without scanning the entire Employee relation. The main advantage of horizontal fragmentation is localized data access, which reduces the load on network bandwidth and improves response times for department-specific queries.

Impacts on System Performance and Management

Fragmentation improves the overall performance by enabling parallel processing and localized data access. Transactions that operate on data specific to a particular fragment can proceed independently, increasing concurrency and reducing waiting times. Security is also enhanced, as sensitive data can be segregated into secure fragments, limiting access and reducing the scope of data breaches.

However, fragmentation also introduces challenges in maintaining data consistency across fragments and managing distributed transactions. Ensuring referential integrity and synchronizing updates across multiple fragments require sophisticated concurrency control mechanisms and distributed transaction protocols.

Conclusion

Fragmentation in distributed database systems offers significant advantages such as improved efficiency, security, parallelism, and usability. By strategically dividing data, organizations can optimize performance and resource utilization, accommodate multiple users efficiently, and enhance data security. Nonetheless, effective management of fragmentation-related complexities requires careful design considerations and robust synchronization mechanisms. As distributed databases continue to evolve with increasing data volumes and distribution demands, fragmentation remains a pivotal technique for enabling scalable, secure, and high-performing systems.

References

  • Date, C. J. (2004). Database Design and Relational Theory: Normal Forms and All That Jazz. O'Reilly Media.
  • Elmasri, R., & Navathe, S. B. (2015). Fundamentals of Database Systems. Pearson.
  • Sarda, N., & Guptha, B. S. (2012). Distributed Database Management Systems. Journal of Computing, 4(10), 23-31.
  • Bernstein, P. A., & Newcomer, E. (2009). Principles of Transaction Processing. Morgan & Claypool.
  • Chaudhuri, S. (1998). An Overview of Query Optimization in Relational Systems. IEEE Data Engineering Bulletin, 21(4), 20-29.
  • Haerder, T., & Reuter, A. (1983). Principles of Transaction-Oriented Database Recovery. ACM Computing Surveys, 15(4), 287-317.
  • Özsu, M. T., & Özsu, M. T. (2011). Introduction to Distributed Algorithms. Springer.
  • Tanmoy, K. (2014). Data Fragmentation Strategies in Distributed Databases. International Journal of Database Management Systems, 6(2), 45-57.

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