DBMS Relational Algebra

Question

Which of the following Queries is more Efficient on the given data?

1. In terms of Space.
2. In terms of Calculation. also, How many calculations are necessary for Each?

 

Answer 1

In terms of space :second relational expression is efficient. Because the final table on which conditions will be applied contains 3 attributes only  whereas in first relational expression the  table on which the conditions are applied will contain more than  3 attributes.  obviously the smaller the table , more space efficient it would be.

and the number of calculations is equal for both the relational expressions .