31. | Student (school-id, sch-roll-no, sname, saddress) School (school-id, sch-name, sch-address, sch-phone) Enrolment(school-id sch-roll-no, erollno, examname) ExamResult(erollno, examname, marks) What does the following SQL query output? SELECT sch-name, COUNT (*) FROM School C, Enrolment E, ExamResult R WHERE E.school-id = C.school-id AND E.examname = R.examname AND E.erollno = R.erollno AND R.marks = 100 AND S.school-id IN (SELECT school-id FROM student GROUP BY school-id HAVING COUNT (*) > 200) GROUP By school-id |
Discuss |
Answer: (d).nothing; the query has a syntax error
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32. | Given the basic ER and relational models, which of the following is INCORRECT? |
Discuss |
Answer: (c).In a row of a relational table, an attribute can have more than one value
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33. | Consider a join (relation algebra) between relations r(R)and s(S) using the nested loop method. There are 3 buffers each of size equal to disk block size, out of which one buffer is reserved for intermediate results. Assuming size(r(R)) < size(s(S)), the join will have fewer number of disk block accesses if |
Discuss |
Answer: (a).relation r(R) is in the outer loop
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34. | Let E1 and E2 be two entities in an E/R diagram with simple single-valued attributes. R1 and R2 are two relationships between E1 and E2, where R1 is one-to-many and R2 is many-to-many. R1 and R2 do not have any attributes of their own. What is the minimum number of tables required to represent this situation in the relational model? |
Discuss |
Answer: (b).3
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35. | In a schema with attributes A, B, C, D and E following set of functional dependencies are given A → B A → C CD → E B → D E → A Which of the following functional dependencies is NOT implied by the above set? |
Discuss |
Answer: (b).BD → CD
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36. | A database of research articles in a journal uses the following schema. (VOLUME, NUMBER, STARTPGE, ENDPAGE, TITLE, YEAR, PRICE) The primary key is (VOLUME, NUMBER, STARTPAGE, ENDPAGE) and the following functional dependencies exist in the schema. (VOLUME, NUMBER, STARTPAGE, ENDPAGE) -> TITLE (VOLUME, NUMBER) -> YEAR (VOLUME, NUMBER, STARTPAGE, ENDPAGE) -> PRICE The database is redesigned to use the following schemas. (VOLUME, NUMBER, STARTPAGE, ENDPAGE, TITLE, PRICE) (VOLUME, NUMBER, YEAR) Which is the weakest normal form that the new database satisfies, but the old one does not? |
Discuss |
Answer: (b).2NF
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37. | Which of the following relational query languages have the same expressive power? 1.Relational algebra 2.Tuple relational calculus restricted to safe expressions 3.Domain relational calculus restricted to safe expressions |
Discuss |
Answer: (d).I, II and III
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38. | A Relation R with FD set {A->BC, B->A, A->C, A->D, D->A}. How many candidate keys will be there in R? |
Discuss |
Answer: (c).3
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39. | What is the min and max number of tables required to convert an ER diagram with 2 entities and 1 relationship between them with partial participation constraints of both entities? |
Discuss |
Answer: (c).Min 2 and max 3
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40. | Relation R has eight attributes ABCDEFGH. Fields of R contain only atomic values. F = {CH -> G, A -> BC, B -> CFH, E -> A, F -> EG} is a set of functional dependencies (FDs) so that F+ is exactly the set of FDs that hold for R. How many candidate keys does the relation R have? |
Discuss |
Answer: (b).4
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