24
Queries
Find all courses that Mary
takes
What happens behind the scene
?
Query processor figures out how
to answer the query efficiently.
SELECT
C.name
FROM Students S, Takes T, Courses C
WHERE S.name=Mary and
S.ssn = T.ssn and T.cid = C.cid
FROM Students S, Takes T, Courses C
WHERE S.name=Mary and
S.ssn = T.ssn and T.cid = C.cid