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DBMS Relational Algebra

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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?

 

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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 .

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