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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.
Types Of Indexes One of the words used during the file organisation is the term index. In this part, let us describe this term in more detail. We find the index of keywords
The Internal or Physical Level The collection of files permanently stored on secondary storage devices is called as the physical database. The internal or physical level is t
Describe Dynamic Model. The dynamic model specifies allowable sequences of changes to the objects from an object model. It contains event trace diagrams describing scenarios. A
Table_Name( attribute_1, attribute_2, attribute_3, ….. ,attribute_x) Primary Key ( attribute_1, attribute_2) Foreign Key attribute_4 References Table_Name_2 (repeat for each fore
Some disadvantages of File Oriented System ?
Primary Index In primary index, there is a one-to-one relationship among the entries in the index table and the records in the major table. Primary index can be of two types:
Define what Immediate database modification technique uses? Ans: Both undo and redo.
differences between a classified catalog and a dictionary catalog
Question: In a multi-user database environment, locking mechanisms can be used to solve the three basic problems of concurrency. On the other hand, however, locking may also le
The insertion of a tuple in the aim of reference does not cause any destruction. Though, insertion of a tuple in the relation in which, we has the foreign key, for instance, in ASS
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