Question

City	Food
Monza	Pasta
Baku	Burger
Baku	Fish
Munich	Pasta
Munich	Fish
Porto	Pizza
CapeTown	Pasta
Cape Town	Fish

Division in RA: The above is a table eats: Which cities eat all the foods eaten in Munich? Be sure to show your work

Answer 1

Solution

Foods eaten in Munich:

π_Food(σ_{City='Munich'}(Eats))

All possiblities of cities and food eaten in Munich

= All Cities X Foods eaten in Munich

= π_City(Eats) X π_Food(σ_{City='Munich'}(Eats))

Cities which do not eat all the foods eaten in Munich

= All possiblities of cities and food eaten in Munich - Actual city, food combination(Eats table)

= π_City(π_City(Eats) X π_Food(σ_{City='Munich'}(Eats)) - π_City,Food(Eats))

Cities which eat all the foods eaten in Munich

= All cites except Munich - Cities which do not eat all the foods eaten in Munich

= π_City(σ_{City!='Munich'}(Eats)) - Cities which do not eat all the foods eaten in Munich

= π_City(σ_{City!='Munich'}(Eats)) - π_City[π_City(Eats) X π_Food(σ_{City='Munich'}(Eats)) - π_City,Food(Eats)]