Query Execution Plans

Purchase

Person

Buyer=name

City=‘seattle’

phone>’5430000’

buyer

(Simple Nested Loops)

SELECT S.sname

FROM Purchase P, Person Q

WHERE P.buyer=Q.name AND

Q.city=‘seattle’ AND

Q.phone > ‘5430000’

?

Query Plan:

• logical tree

• implementation choice at every node

• scheduling of operations.

(Table scan)

(Index scan)

Some operators are from relational

algebra, and others (e.g., scan, group)

are not.

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