Query Optimization

Purchase

Person

Buyer=name

City=‘seattle’

phone>’5430000’

buyer

(Simple Nested Loops)

Imperative query execution plan:

SELECT S.sname

FROM Purchase P, Person Q

WHERE P.buyer=Q.name AND

Q.city=‘seattle’ AND

Q.phone > ‘5430000’

Declarative SQL query

Plan: Tree of R.A. ops, with choice of alg for each op.

Ideally: Want to find best plan. Practically: Avoid worst plans!

Goal:

?

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