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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 is meant by buffer blocks and disk buffer The blocks residing temporarily in main memory are referred to as buffer blocks. The area of memory where blocks reside t
Which operation is used if we are interested in only certain columns of a table? PROJECTION operation is used if we are interested in only certain columns of a table.
Write the motivations led to development of OO-DBMS? 1. Programmer frustration with RDBMSs. 2. Requirement for special features.
Describe the four main ways of optimising disk block access. Ans: a. Disk b. Non-volatile writes buffers c. File organization (Clustering) d. Log-based file system
What is the disadvantage of a call by reference? During a call by reference damage or loss of data is not restricted to the subroutine, but will instantly lead to alters to th
Define reference file
What is the meaning of Data independence? Data independence means a programs that are not dependent on the physical attributes of data and a programs that are not dependent on
The following data are required to be stored by a family physician. Family#, FamilyAddress, Patient#, PatientName, ServiceCode, ServiceFee, ServiceDate A family can have seve
What are the uses of the information in the Data dictionary? The following information is directly taken from the Data dictionary: Information on fields displayed with
Removing a Synonym: DROP SYNONYM D30;
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