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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.
What is difference between primary index and secondary index? Primary Index a) It is an ordered file whose records are of fixed length along with two fields. b) Only base
What is the aim of logical schema ? The main motive of the logical schema is to ensure the portability of procedures and models on various physical schemas at runtime.
Define Query Processing Query processing is the process of selecting the best plan or strategy to be employed in responding to a database request. The plan is then executed to
Rules Of Data Normalisation Let us now summarise Normalisation with the help of various clean rules. The following are the necessary rules for the Normalisation process: 1.
Outer Join: The use of Outer Join is that it still joins those tuples that do not have matching values in common columns are also contained in the result table. Outer join places
why are older data models are being replaced by new data models
What are uncommitted modifications? The immediate-modification technique permits database modifications to be output to the database whereas the transaction is still in the act
Why is need for the multiple access paths?
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What are data models? Explain it detail? Entity relationship model Rectangles Ellipse Diamonds Lines Relational model Relational model use a collection
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