GATE | GATE 2017 MOCK II | Question 55
A student relation with 4 attributes is defines as R(ABCD). Which of the following query will execute without error if all attributes are numeric.
(A) Only A
(B) Only B
Explanation: Query in A is correct. It will first select required rows and then project required columns. But query in B is not correct as after projecting B and C columns, it can’t have row selection based on condition on attribute A. So correct option is 1.
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