# Databases - Relational Calculus

# Databases - Relational Calculus

+ 0 comments Here is my stab at the logic, derived from giyam's answers below and Googling set notation:

**Give me the set of x such that for all y***in set(x) and set(y)*is a function of (where) y <= xHowever, I think the italicized section above is unclear due to the nature of the problem as it is written...that is, what is the relationship with y and 'S(x)' after ∀?

Definitions:

*∀ = forall*(https://en.wikipedia.org/wiki/Turned_A)*| = such that*(https://en.wikipedia.org/wiki/Set-builder_notation)*∧ = logical conjunction (and)*(https://en.wikipedia.org/wiki/List_of_logic_symbols)*→ = is a function from*(https://math.stackexchange.com/questions/1740154/different-arrows-in-set-theory-rightarrow-and-mapsto)

+ 0 comments find a specific x in set S which all numbers y in S are less or equal to x.

+ 0 comments That's super weird notation. Why not use , also there should probably a colon or dot or space after the .

+ 0 comments Simplifying the Relational Calculus expression in plain language, the question can be translated as follows:

*" Find an element in set X, such that for all elements in Set(X) and Set(Y), there is a function where y is less than or equal to x "*So all in all, we demand a set element from S (say x) whose valueis always greater than or equal to y. Logically, the greatest element in the given set S will be the element x needed as an answer since no other element can be greater than that.

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