domain relational calculus "for all" expression -


i have database of university below:

student (sid, name, family, mean, age, city, street, cid) instructor (iid, name, family, salary, city, street, cid) college (cid, name, city)

how can answer following query in domain relational calculus (drc) ?

"find instructors in all colleges located in london"

find instructors such there not exist college located in london such instructor not in college.

but question bit questionable given db structure seems allow instructor "be in" @ 1 single college, @ time.


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