Question

SELECT operation in SQL is equivalent to
1. the selection operation in relational algebra
2. the selection operation in relational algebra, except that SELECT in SQL retains duplicates
3. the projection operation in relational algebra
4. the projection operation in relational algebra, except that SELECT in SQL retains duplicates

Answer 1

Correct Answer - Option 4 : the projection operation in relational algebra, except that SELECT in SQL retains duplicates

Select operation is equivalent to the projection operation in relational algebra, except that select in SQL retains duplicates and on the contrary projection removes the duplicates.