Consider that the relation has only one attribute $A$.

@shashin, Yes I agree that we can translate RA to sql.

But as far as I know RA query only takes relation as input and gives relation as output and this relation is set of tuples.

So I thought that relation should not include any duplicate.

@Vimal Patel - does this help ?

https://www2.cs.sfu.ca/CourseCentral/354/zaiane/material/notes/Chapter4/node11.html

Formal query languages are based on mathematical relations. Thus no duplicates appear in relations. As duplicate removal is expensive, SQL allows duplicates.

Here we are just told 'relations' - so we assumed a practical implementation that mostly allows duplicates. From a purely mathematical perspective - no duplicates. What say ?

404 Points

198 Points

126 Points

67 Points

20 Points

12 Points

10 Points

7 Points

6 Points

203 Points

156 Points

143 Points

49 Points

16 Points

15 Points