DBMS |Gate-2007| Previous Year Questions| Set-14

Set-15 GATE-2006 DBMS

DBMS |Gate-2007| Database Management System

1. Consider the following relation schemas :

i. b-Schema = (b-name, b-city, assets)
ii. a-Schema = (a-num, b-name, bal)
iii. d-Schema = (c-name, a-number)

Let branch, account and depositor be respectively instances of the above schemas. Assume that account and depositor relations are much bigger than the branch relation. Consider the following query: Пc-name (σb-city = “Agra” bal < 0 (branch ⋈ (account ⋈ depositor) Which one of the following queries is the most efficient version of the above query ?  [GATE – 2007]

a. Пc-name (σbal < 0 (σb-city = “Agra” branch ⋈ account) ⋈ depositor)
b. Пc-name (σb-city = “Agra”branch ⋈ (σbal < 0 account ⋈ depositor))
c. Пc-name (σb-city = “Agra” branch ⋈ σb-city = “Agra” ⋀ bal < 0 account) ⋈ depositor)
d. Пc-name (σb-city = “Agra” ⋀ bal < 0 account ⋈ depositor))

Answer  : a)


2. Consider the following implications relating to functional and multivalued dependencies given below, which may or may not be correct. i. If A ↠ B and A ↠ C then A → BC ii. If A → B and A → C then A ↠ BC iii) If A ↠ BC and A → B then A → C iv) If A → BC and A → B then A ↠ C Exactly how many of the above implications are valid? [GATE – 2007]

a. 0
b. 1
c. 2
d. 3

Answer : c)


3. Consider a selection of the form σA≤100(r), where r is a relation with 1000 tuples. Assume that the attribute values for A among the tuples are uniformly distributed in the interval [0, 500]. Which one of the following options is the best estimate of the number of tuples returned by the given selection query ? [GATE – 2007]

a. 50
b. 100
c. 150
d. 200

Answer : d)


4. Consider the following schedules involving two transactions. Which one of the following statements is TRUE? [GATE – 2007]

a. Both S1 and S2 are conflict serializable.
b. S1 is conflict serializable and S2 is not conflict serializable.
c. S1 is not conflict serializable and S2 is conflict serializable.
d. Both S1 and S2 are not conflict serializable.

Answer : c)


5. The order of a leaf node in a B+– tree is the maximum number of (value, data record pointer) pairs it can hold. Given that the block size is 1K bytes, data record pointer is 7 bytes long, the value field is 9 bytes long and a block pointer is 6 bytes long, what is the order of the leaf node? [GATE – 2007]

a. 63
b. 64
c. 67
d. 68

Answer : a)


6. Which one of the following statements if FALSE? [GATE – 2007]

a. Any relation with two attributes is in BCNF
b. A relation in which every key has only one attribute is in 2NF
c. A prime attribute can be transitively dependent on a key in a 3NF relation
d. A prime attribute can be transitively dependent on a key in a BCNF relation

Answer : d)
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