# Questions tagged [tuple-relational-calculus]

The tag has no usage guidance.

13 questions
Filter by
Sorted by
Tagged with
23 views

### Tuples excludes by making them evaluate automatically to TRUE (Relational Calculus)

I've put a lot of effort into understanding this query statement and it just doesn't make sense. ...
1 vote
30 views

### 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 ...
76 views

### 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 ...
1 vote
141 views

### 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 ...
1 vote
493 views

### Division in tuple relational calculus

$\newcommand{\Set}{% \{\, #1 \mid #2 \, \}% }$ I've been trying to find how to express relational division operation in tuple relational calculus. The only thing I found is this presentation ...
280 views

### 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 ...
82 views

### 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: ...
98 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., ...
100 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 ...
2k views

### 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 ...
1 vote
1k 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 ...
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 ...