Given a column with some duplicated values, how does one go about pulling out a subset of that column with all the unique values in it?
E.g: Given the relation Serves with attributes [pizzeria_name, pizza_name, price], I'm interested in knowing the names of the pizzas whose prices are under $10 everywhere they are served.
I can do a selection to get pizzas under $10, and I can project the names into a column, but I have no idea how to get the unique names only.
EDIT: I think I might be retarded and the relational algebraic projection actually already takes care of this.
E.g: Given the relation Serves with attributes [pizzeria_name, pizza_name, price], I'm interested in knowing the names of the pizzas whose prices are under $10 everywhere they are served.
I can do a selection to get pizzas under $10, and I can project the names into a column, but I have no idea how to get the unique names only.
EDIT: I think I might be retarded and the relational algebraic projection actually already takes care of this.