GATE CSE 2007
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MCQ (Single Correct Answer)
GATE CSE 2007
Consider the following relation schemas :
b-Schema = (b-name, b-city, assets)a-Schema = (a-num, b-name, bal)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 LESS THAN 0 (branch ⋈ (account ⋈ depositor)
Which one of the following queries is the most efficient version of the above query ?(A) Пc-name (σbal LESS THAN 0 (σb-city = “Agra” branch ⋈ account) ⋈ depositor)(B) Пc-name (σb-city = “Agra”branch ⋈ (σbal LESS THAN 0 account ⋈ depositor))(C) Пc-name (σb-city = “Agra” branch ⋈ σb-city = “Agra” ⋀ bal LESS THAN 0 account) ⋈ depositor)(D) Пc-name (σb-city = “Agra” ⋀ bal LESS THAN 0 account ⋈ depositor))