GATE CS Integrity Constraints questions

Consider the following statements $S1$ and $S2$ about the relational data model: $S1$: A relation scheme can have at most one foreign key. $S2$: A foreign key in a relation scheme $R$ cannot be used to refer to tuples of $R.$ Which one of the following choices is correct?

Consider the following tables $T1$ and $T2.$ …

Given an instance of the STUDENTS relation as shown as below …

The maximum number of superkeys for the relation schema $R(E,F,G,H)$ with $E$ as the key is _____.

A prime attribute of a relation scheme $R$ is an attribute that appears

Consider a relation scheme $R = (A, B, C, D, E, H)$ on which the following functional dependencies hold: {$A \rightarrow B$, $BC \rightarrow D$, $E \rightarrow C$, $D \rightarrow A$}. What are the candidate keys R?

The following table has two attributes $A$ and $C$ where $A$ is the primary key and $C$ is the foreign key referencing $A$ with on-delete cascade. …

Let $R (a, b, c)$ and $S(d, e, f)$ be two relations in which $d$ is the foreign key of $S$ that refers to the primary key of $R$. Consider the following four operations $R$ and $S$ Insert into $R$ Insert into $S$ Delete from $R$ Delete from $S$ Which of the following can cause violation of the referential integrity constraint above?