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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.
Describe Interfaces for the DBA? Interfaces for the DBA - Most database systems holds privileged commands which could be used only through the DBA's staff. These involves com
Question: (a) e-Government implementations normally evolve through a multi-stage process. Describe, using appropriate examples, the stages involved in an e-Government implemen
Describe integrity and security? a) Domain constraint b) Referential integrity A value that appears in one relation for a given set of attributes also appear fo
what is data link layer
What is an index? An index is a structure that helps to place desired records of a relation quickly, without probing all records.
Compute the closure (F+) for the following set of the functional dependencies defined on R(a,b,c,d), where F - {c→ a, ab → d, a → b, d → c}, i.e. what are all of the FDs implied b
Discuss the count function? The COUNT function used returns the number of tuples or values fixed in a query. The count function comprises two types of syntax: (1) COUNT (*)
Shared lock or Read Lock It is requested by a transaction that needs to just read the value of data item. A shared lock on a data item does not permit an exclusive lock
What is Candidate Key Super Key or Candidate Key: It is such an attribute of a table that can uniquely recognize a row in a table. Generally they have unique values and can n
The data of a view is not physically stored, but derived from one or more tables. True the data of a view is not physically stored
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