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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.
statical data
Failures and Recovery In practice various things might occur to prevent a transaction from completing. Recovery methods are used to bring database, which does not satisfy consi
What is document scanning and imaging? Document scanning and imaging, or digital archiving, is the method of scanning a document into a digital image to archive and retrieve a
1. Define each of the following IN YOUR OWN WORDS: (a) File: (b) Record: (c) Field: (d) Primary Key: (e) Secondary Key: 2. A travel agency wants t
What is Foreign Key Foreign Key: Sometimes we may have to work with an attribute that does not have a primary key of its own. To recognize its rows, we have to use the primar
E-R model uses this symbol to represent weak entity set ? A Doubly outlined rectangle symbol is used to represent weak entity set.
what is the need of a log in dbms
The Conceptual Level or Global level The conceptual level presents a logical view of the complete database as a unified whole. It permits the user to bring all the data in th
What is object containment? References among objects can be used to model dissimilar real-world concepts.
1. Which model is used to store data in tree structures Ans: Hierarchical model is used to store data in tree structures
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