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(a) Design a query plan for the following distributed query: An application at site B wants to compute a join of STUDENT ?Id=StudId TRANSCRIPT where STUDENT (Id,Major) is at site B and TRANSCRIPT (StudId, CrsCode) is at site C. The result should be returned to B. Assume that semijoin is not used. Also assume that
(b) Estimate the cost of computing σMajor='CS' (STUDENT) ?Id = StudId TRANSCRIPT using the semijoin strategy. Use the sizes of the STUDENT and TRANSCRIPT relations and of their attributes from the part (a) above. In addition, assume that 10% of the students major in CS. Compare this with the solutions in part (a) above that do not use the semijoin.
Explain the Weak Entity Set An Entity set which does not have sufficient attribute to make a primay key is known as weak entity set. For instance, dependents of an employee in
How many levels can be viewed in Architecture of the database ? Architecture of the database can be viewed as three levels.
Primary Key The primary key is the candidate key that is selected by the database designer as the principal denotes of identifying entities within an entity set. The left candi
What is the difference between internal tables and extract datasets? The lines of an internal table always have the similar structure. By using extract datasets, you can ha
XYZ is a large chain of home entertainment rental over 100 stores distributed over all states in Australia. XYZ lends entertainment products such as movies, TV shows and games on v
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Question: i) Explain the terms data warehousing and data mining. ii) Discuss the importance of the following security principles that a digital firm should amongst others, n
How to create a table from existing table? Create table as e.g, To create a new table ‘N_emp' with employee names and their identification numbers only from employee ta
Entity types that do not have any key attribute, and therefore cannot be identified independently, are known as weak entity types. A weak entity can be recognized uniquely only by
What is a recursive relationship? Give an example not used in the text. A recursive relationship is a relationship among an entity and itself. For example, given the entity PER
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