SQL Schemas:

Beers(name, manf)

Bars(name, addr, license)

Drinkers(name, addr, phone)

Likes(drinker, beer)

Sells(bar, beer, price)

Frequents(drinker, bar)

In MYSQL query, express the following: 2. Drinkers who like some beers which John also likes 

3. Pairs of drinkers and bars such that a drinker frequents the bar and the bar serves at least one beer which the drinkerlikes

4. Bars which are frequented by John or Rebecca but not by both of them