Questions tagged [tuple-relational-calculus]
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12 questions
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Relational calculus: "Find all X with at least y amount of Z"
Assuming I have two relations:
Supplier [ID (PK), Name, City, Country] and
Item [ID (PK), Name, Department, Price, Stock, Supplier_ID (FK)]
What would be the easiest way to determine the following ...
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Can quantifiers be used on variables bound on the left side of the pipe in Tuple Relational Calculus?
Our professor has solved an example for us. They taught us it's incorrect to use a quantifier (exists or forall) with a variable ...
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division expression in tuple relational calculus
Could someone please explain the expression for division in tuple relational calculus in words? I do not understand how the multiple operators (existential and universal quantifiers) are to be ...
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Division in tuple relational calculus
$ \newcommand{\Set}[2]{%
\{\, #1 \mid #2 \, \}%
}$
I've been trying to find how to express relational division operation in tuple relational calculus. The only thing I found is this presentation ...
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Intuition for a projection in tuple relational calculus
Let's have a relation $R = (name, surname, age)$. I want to obtain a new relation with only the $name$ attribute. In relational algebra I would simply do $\Pi_{\mathrm{name}}(R)$ but in relational ...
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Tuple relational calculus: existential quantifiers
I have the following question and given answer:
Question: List the names of managers who have at least one dependant.
Answer: ...
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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., ...
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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 ...
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Is it possible to do a NULL comparison in Relational Algebra?
Please consider the following question given in a booklet:
I have read about databases from Database System Concepts - by Henry F. Korth, but never saw an instance where we could do a NULL comparison ...
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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 ...
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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 ...
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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 ...
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