# Questions tagged [relational-calculus]

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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., ...
48 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 ...
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### 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 ...
75 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 ...
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### 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, ...
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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 ...
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 ...