Hi
I have a question I need to answer for an assignment.
Here is the databse schema:
Code:
LIKES(drinker,beer);
FREQUENTS(drinker,bar);
SERVES(bar,beer,cost);
The question is:
Code:
Find bars that serve at least one beer liked by Joe, but do not serve any beer liked by
Michael.
Here is what I have:
Code:
SELECT S.bar
FROM LIKES L, SERVES S
WHERE L.beer = S.beer AND L.drinker='Joe'
EXCEPT
SELECT S.bar
FROM LIKES L , SERVES S
WHERE L.beer = S.beer AND L.drinker='Michael'
Does this look ok? I am not sure if this enforces the 'at least one beer' constraint.
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SQL Assignment help
10-07-11, 10:38
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