Question

Query to find “All bars that sell three different beers at the same price?”

My Tables are

Sells(bar,beer,price) – bar – foreign Key..
Bars(name,addr) – name primary key.

I thought of something like this but that dosent seem to work …

 Select A.bar As bar , B.bar as bar  
 From Sells AS A, Sells AS B 
 Where A.bar = B.bar and A.beer <> B.beer  
 Group By(A.beer) 
 Having Count(Distinct A.beer) >= 2

Is this the correct SQL query ?

Answer 1

I would do it this way:

Select A.bar
From Sells AS A
JOIN Sells AS B ON (A.bar = B.bar AND A.price = B.price 
    AND A.beer <> B.beer)
JOIN Sells AS C ON (A.bar = C.bar AND A.price = C.price 
    AND A.beer <> C.beer AND B.beer <> C.beer)

In MySQL in particular, the join solution is likely to be more efficient than GROUP BY.