Questions tagged [relational-calculus]
The relational-calculus tag has no usage guidance.
9
questions
1
vote
1answer
39 views
Check if a relation is reflexive, symmetric and transitive
I want to better understand how this actually works, as my solutions are
sometimes not 100% correct.
I have the following relation:
Check if the following relation is reflexive, symmetric, and/or
...
0
votes
0answers
18 views
Relation Closure for F+
$A \rightarrow B C$
$C D \rightarrow E$
$B \rightarrow D$
$E \rightarrow A$
I have these Relations for R={A,B,C,D,E}
Now I have to calculate the closure $F^+$ and give the candidate keys
I came ...
0
votes
1answer
62 views
Need help understanding the tuple relational calculus
We say that a query in a TRC is a statement of the form $\{T: P(T)\}$, where $T$ is a tuple variable and $P(T)$ is a formula.
Now my question is, what are the possible tuples $T$ to be tested i.e., ...
0
votes
1answer
79 views
Normal form after decomposition of a relation
I came across a text recently which claims that if we perform a lossless decomposition of a relation R into smaller relations R1 and R2, and if R is in 3NF, both R1 and R2 are 3NF.
I felt a bit ...
0
votes
1answer
55 views
Whether same output is obtained for the two queries
Consider the following SQL Queries executed on the relation Employee:
Employee (Eid, Ename, sal)
Eid is the primary key
Queries:
S1:SELECT count (*) FROM Employee;
S2: SELECT count (Eid) FROM ...
0
votes
1answer
71 views
Normal form of relation R
It is given that for a relation R all the attributes of the relation appear in some of the candidate keys. It is also given that there is only one compound candidate key which exists for a relation, ...
1
vote
1answer
739 views
Relational calculus to SQL
I am somewhat aware of the correspondence between (tuple and domain) relational calculus, relational algebra, and SQL. To the best of my understanding, one should be able to automatically convert a ...
0
votes
0answers
106 views
Relational calculus expression for projection (Database Management)
I recently came across this question:
Let the following relation schemas be given:
$R=(A,B,C)$
$S=(D,E,F)$
Let relations r(R) and s(S) be given. Give an expression in the tuple relational
calculus ...
0
votes
1answer
263 views
Use of existential quantifier in tuple relational calculus
It is somewhat confusing to me when to use quantifiers in tuple relational calculus (TRC). I stumbled upon following problem and I am still scratching my head thinking why not TRC query can be ...
