find the number of tuples

Question

Given enroll table as follows:

What is the number of tuples in the output of the following query?
Select Stud.Id FROM ENROLL WHERE grade = ‘A’
UNION ALL
Select Stud.Id FROM ENROLL WHERE grade = ‘B’;

in this table ,select operation will select distinct student id values or it can take same studentid wherever grade = A or B??

i.e

first select operation on A will select (1,2,3) or (1,2,1,3)  ??

Comments

is it 7

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i dun know the xact answer..may be it as given as 7 but how come it is 7..?check my below comment

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@prabhanjan_1 ,,then what should be the answer..?7 or 10??

Answer 1

Result will be six tuples from the above query.

Comments

how u got 6?

first select will give {1,2,1,3}

second will give {1,1,2,4,5,1}

their union will not remove duplicates.so asnwer should be 10.how is it 6?