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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.
A super key is an attribute or set of attributes used to recognize the records uniquely in a relation. For instance, in the Relation PERSON defines earlier PERSON_ID is a super
What are wait-for-graphs?Give the algorithm to construct a wait-for-graph from a given schedule of transactions? How can deadlocks be detected from wait-for-graphs? Ans: The
What are the different approaches for database design? There are two basic approaches for database design which are as follows: Attribute driven: It compiles a list of att
Security: In a centralised system, access to the data can be simply controlled. Though, in a distributed DBMS not only does access to replicated data have to be controlled in many
Replicating Data One approach that may support efficient access to dissimilar applications as above may be to give access to every of the applications from dissimilar replicate
What is data definition language? Explain it in detail? The SQL DDL allows specification of not only a set of relations, but also information after each relation, containing
Entities Let us first be aware of the question: What are entities? An entity is an object of concern used to show the things in the actual world, e.g., table, car, bo
Database Administrator One of the main perpose for having the database management system is to have control of both data or programs accessing that data. The person having li
What is persistency? Persistency ensures which data is stored and that after the object is no longer available (program stops running) the data will be available to other users
We are looking to find someone to prepare a database which improves upon the one we are using at present. The present database will be found here: Click on filter options and yo
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