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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.
Log based recovery: Let us first describe the term transaction log in the context of DBMS. A transaction log is a record in DBMS that remains track of all the transactions of a dat
Define Atom of domain relational calculus An atom has the outline 1 , x 2 , ... , x n > -> r , in which r stands for a relation on n attributes and x 1 , x 2 , ... , x n ar
A Structure of a dependency diagram
Discuss the problem of Spurious tuples and how we may prevent it. Ans: A spurious tuple is, mainly, a record in a database that gets created while two tables are joined bad
Explain about database system structure? Storage manager Authorization and integrity manager Transaction manager File manager Buffer manager Storage manager
Benefits and limitations
Define the terms 1) physical schema 2) logical schema. Physical schema: The physical schema explains the database design at the physical level, which is the lowest level of abs
Foreign Keys and NULL Let us take the relation: DEPT DEPT ID DNAME BUDGET D1 M
Define Outer join Outer join - If there are any type of values in the one table that do not have corresponding value(s) in the other, in an equi-join which will not be selected
Describes the several relationship constraints through giving suitable example? Constraints on relationships: There are two kinds of constraints on relationships. 1) Mapping
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