Consider the join graph and the following information sizeEM

Consider the join graph and the following information:

size(EMP) = 100, size(ASG) = 200, size(PROJ) = 300, size(EMP 1 ASG) = 300,

and size(ASG 1 PROJ) = 200. Describe an optimal join program based on the

objective function of total transmission time.

Solution

natural join if u taking it takes only the common attributes so as

size(emp)=100, size(asg)=200, size(proj)=300

size(asg natural join proj)= 200 thats why only common attributes were taken

size(emp union asg)=300 total join where the union is done among two tables

optimal join is the natural join so only common attributes must be taken)

size(emp * asg * proj) =100 the min value is 100 so the max common attributes among all three can be 100 only .