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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.
What are the ways in which signal can be generated A signal might be generated in many ways such as a Signal is result of particular physical condition. Whenever a process writ
Logical Operators Rules of Precedence: Order evaluated Operator 1 All comparison operators 2
Set Difference If R1 and R2 are two union compatible relations or relations then result of R3 =R1- R2 is the relation that have only those tuples that are in R1 but not in R2.
What is called remapping of bad sectors? If the controller detects that a sector is injured when the disk is initially formatted, or when an attempt is made to write the secto
Use a Set operator to create a list of academics who have written or co-written less than 5 papers and also have greater than 3 interests. List their academic number in the output.
What do you understand by a view? What does WITH CHECK OPTION clause for a view do? - A view is a virtual table which comprises fields from one or more real tables. - It is
Explain Superkey Ans: A superkey is described in the relational model of database organization like a set of attributes of a relation variable for which it holds that in all re
Question: (a) One of the steps in the five-step problem-solving model is implementation. Implementation is considered a key step in the problem-solving model. A problem may be
What are the time stamps associated with each data item? W-timestamp (Q) denotes the largest time stamp if any transaction that implemented WRITE (Q) successfully. R-timesta
Explain the θ-join and equijoin Refer tables Car and Boat which list models of cars and boats and their relevant prices. Assume a customer wants to buy a car and a boat, but sh
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