# Databases - Relational Calculus

# Databases - Relational Calculus

ramey_steven + 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)

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

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

shubham_mahawar + 1 comment Not understand the question properly It looks like find x from s(x) and y from s(y) and check y<=x

then there are many possible combination of this as 3<=3,4,5,6,7,10,11,19,18 4<=4,5,6,7,10,11,19,18 5<=5,6,7,10,11,19,18 6<=6,7,10,11,19,18 7<=7,10,11,19,18 10<=10,11,19,18 11<=11,19,18 18<=18,19 19<=19

total 45 but it is wrong anyone explain plz

matt_irby + 0 comments I'm going to take my stab at rephrasing the formula as it tripped me up to.

It's asking to find an x in S such that any y in S means y <= x.

So, it's asking which element in S is greater than or equal to any other element in S, including itself? This would be 19 because it is the greatest element in the set, therefore it is greater than or equal to all the other elements in the set.

imtiazu8 + 0 comments what is basically x and y here, so that y<=x?

sai_jeelakarra + 0 comments the answer is 19 beczz the maximum value of x for any y<=x in s is 19

yashtrivedi7_yt + 0 comments It is basically asking to find out the largest number in the set for x so x may be equal to y or greater than it I still havent deciphered the exact statement in terms of words like x or y in the sample space x...

Please if anyone give me the exact relational statement and don't point to wiki pages as i have spent a lot of time researching this and haven't found the exact answer

amitrapstar + 2 comments CAN ANYBODY EXPLAIN ME THE RELATION PLEASE.

yogesh_suthar + 1 comment x such that for every y where S(x) means x belongs to S and S(y) means y belongs to S implies y <= x is true

mobradovic + 0 comments [deleted]

shivu_narang + 1 comment can you help me to get answer? I didnt understand

Adil_MuthukoyaAsked to answer + 3 comments Its actually finding the biggest number in the set , that is you have to find the value of X such that for every Y, X must be greater than or equal. in all (X,Y) pairs

shivu_narang + 1 comment can you help me out? I am not able to do it.... please give me an example to do this

Adil_Muthukoya + 0 comments its about understanding the expression in the question . https://en.wikipedia.org/wiki/Boolean_algebra this link may help you

giaym + 0 comments give me x, that belongs to S, that is greater than y, that belongs to S, for every value of y

is that reading correct? never done this

Soniabhishek36 + 1 comment can you please explain it here ?

giaym + 1 comment a) x| -> give me x

b) Vy -> for all possible values of y //missing a comma or something to separate from the rest, i got lost reading that

c) S(x) -> x is part of the set S (x values come from S)

d) ^ -> and

e) S(y) -> y is part of the set S (y values come from S)

f) -> -> such as, just another condition

g) y <= x -> y is <= x

so you grab a value of x from S (c), and check (f,g) against every y value from S (b,d,e), if it passes, then success (a)

mainak_bhadra + 0 comments very good explanation. it helped me solve the problem. Thank you

No more comments

Sort 9 Discussions, By:

Please Login in order to post a comment