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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.
The PROJECT operation The project operation is used to choose the records with specified attributes as discarding the others based on some related criteria. This is denotes as ∏
How does the two phase protocol ensure serializability in database schedules? Ans: A transaction is termed to follow the two-phase locking protocol if all locking operations
What are domain constraints? A domain is a set of values that might be assigned to an attribute .all values that appear in a column of a relation must be taken fro
List any eight applications of DBMS. a) Universities b) Airlines c) Banking d) Credit card transactions e) Tele communication f) Sales g)Finance h) Manufac
Explain the difference between optimistic locking and pessimistic locking. Optimistic locking supposes no transaction conflict will occur and deals with the consequences if it
1. Staff (staffID --> availabilityID) 2. Services (servicesID --> itemBasedID --> timedBasedID) 3. TimedBased (timedbasedID--> priceid) 4. Clients (clientId, serviceId-->
What is called mirroring? The simplest approach to introducing redundancy is to duplicate each disk. This method is called mirroring or shadowing.
sy bcs project of hospital managment system
Explain concurrency control? Concurrency control Oracles multiversion concurrency control varies from the concurrency mechanism used by some other data base vendors. Read
The Database administrator (DBA) uses the data dictionary in each phase of a database life cycle, beginning from the data gathering phase to the design, execution and maintenance p
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