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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.
To do the division operation R1 ÷ R2, R2 should be a correct subset of R1. In the following example R1 have attributes A and B and R2 have only attribute B so R2 is a correct subse
When a function module is activated syntax checking is performed automatically. YEs, a function module is activated syntax checking.
Describe five main functions of a database administrator. Ans: A database administrator (DBA) is a person who is accountable for the environmental aspects of a database. Genera
You group has been hired by TrainingrUs.com to keeps track of training revenues. TrainingrUS.com wants you to keep scheduling. COURSE table contains following information:
What are the categories of SQL command? SQL commands are separated in to the following categories: 1. Data - Definitition Language 2. Data Manipulation language 3. Dat
Although how will the system recover The selection of REDO or UNDO for a transaction for the recovery is completed on the basis of the state of the transactions. This state is
For each 1: n relationship type R involving two entities E1 and E2, we recognize the entity type (say E1) at the n-side of the relationship type R and contain primary key of the en
How does a query tree represent a relational algebra expression? Discuss any three rules for query optimisation, giving example as to when should each rule be applied. Ans
What do you understand by transitive dependencies? Define with an example any two problems that can take place in the database if transitive dependencies are available in the datab
Determine the Other System Design Issue How to realise subsystems; through hardware or software? How is object model mapped on chosen hardware software? Mapping
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