05 Optimization

Question 1

Estimation selectivity constant attribute selection

Answer 1

sel(att=constant)=1/|att|

Question 2

Estimation selectivity range selection

Answer 2

sel(att in Range)=|range|/|att|

Question 3

Estimation selectivity select AND

Answer 3

sel(p1 AND p2)=sel(p1) * sel(p2)

Question 4

Estimation selectivity select OR

Answer 4

sel(P1 OR p2)=sel(p1)+sel(p2)-sel(p1)*sel(p2)

Question 5

Estimation selectivity join with primary key R.a and foreign key S.b

Answer 5

sel(R j S)=|S|/(|R|*|S|)

Question 6

Estimation selectivity join R.a and S.b without foreign key

Answer 6

sel(R j S)=1/max(|a|, |b|)

Question 7

Estimate output size selection

Answer 7

|select_p(R)|=|R|*sel(p)

Question 8

Estimate output size join

Answer 8

|R j S|=|R||S|sel(R j S)