GATE CS Databases questions

Consider the following two tables and four queries in SQL. Book (isbn, bname), Stock(isbn, copies) Query 1: SELECT B.isbn, S.copies FROM Book B INNER JOIN Stock S ON B.isbn=S.isbn; Query 2: SELECT B.isbn, S.copies FROM Book B LEFT OUTER JOIN Stock S ON B.isbn=S.isbn; Query 3: SELECT B.isbn, S,copies FROM Book B RIGHT OUTER JOIN Stock S ON B.isbn=S.isbn Query …

Consider a database that has the relation schema CR(StudentName, CourseName). An instance of the schema CR is as given below. …

In a database system, unique timestamps are assigned to each transaction using Lamport's logical clock. Let $TS(T_{1})$ and $TS(T_{2})$ be the timestamps of transactions $T_{1}$ and $T_{2}$ respectively. Besides, $T_{1}$ holds a lock on the resource $R,$ and $T_{2}$ has requested a conflicting lock on the same resource $R.$ The following …

Consider a database that has the relation schemas EMP(EmpId, EmpName, DeptId), and DEPT(DeptName, DeptId). Note that the DeptId can be permitted to be NULL in the relation EMP. Consider the following queries on the database expressed in tuple relational calculus. {$t$ | $\exists$u $\in$ EMP(t[EmpName] = u[EmpName] $\wedge$ $\forall$v $\in$ …

Consider a database that has the relation schema EMP (EmpId, EmpName, and DeptName). An instance of the schema EMP and a SQL query on it are given below: …

The following functional dependencies hold true for the relational schema $R\left \{V,W,X,Y,Z \right \}$: $V \rightarrow W$ $VW \rightarrow X$ $Y \rightarrow VX$ $Y \rightarrow Z$ Which of the following is irreducible equivalent for this set of functional dependencies?

Two transactions $T_1$ and $T_2$ are given as $T_1:r_1(X)w_1(X)r_1(Y)w_1(Y)$ $T_2:r_2(Y)w_2(Y)r_2(Z)w_2(Z)$ where $r_i(V)$ denotes a $\textit{read}$ operation by transaction $T_i$ on a variable $V$ and $w_i(V)$ denotes a $\textit{write}$ operation by transaction $T_i$ on a variable $V$. The total number of conflict serializable …

In a $B^+$ Tree , if the search-key value is $8$ bytes long , the block size is $512$ bytes and the pointer size is $2\;\text{B}$ , then the maximum order of the $B^+$ Tree is ____

Consider the following database table named $\text{top\_scorer}$. …

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

An ER model of a database consists of entity types $A$ and $B$. These are connected by a relationship $R$ which does not have its own attribute. Under which one of the following conditions, can the relational table for R be merged with that of A?

Consider the following two phase locking protocol. Suppose a transaction $T$ accesses (for read or write operations), a certain set of objects $\{O_1,\ldots,O_k \}$. This is done in the following manner: $\text{Step 1}$. $T$ acquires exclusive locks to $O_1,\ldots,O_k$ in increasing order of their addresses. $\text{Step 2}$. The required …

Which one of the following is NOT a part of the ACID properties of database transactions?

Which of the following is NOT a superkey in a relational schema with attributes $V,W,X,Y,Z$ and primary key $V\;Y$?

Consider the following database table named water_schemes: …

Consider the following database schedule with two transactions $T_{1}$ and $T_{2}$. $S= r_{2}\left(X\right); r_{1}\left(X\right); r_{2} \left(Y\right); w_{1} \left(X\right); r_{1} \left(Y\right); w_{2} \left(X\right); a_{1}; a_{2}$ Where $r_{i} (Z)$ denotes a read operation by transaction $T_{i}$ on a variable $Z$, $w_{i}(Z)$ denotes a write …

B+ Trees are considered BALANCED because.

Suppose a database schedule $S$ involves transactions $T_1,\ldots,T_n$ . Construct the precedence graph of $S$ with vertices representing the transactions and edges representing the conflicts. If $S$ is serializable, which one of the following orderings of the vertices of the precedence graph is guaranteed to yield a serial schedule?

Consider an Entity-Relationship $(\text{ER})$ model in which entity sets $E_{1}$ and $E_{2}$ are connected by an $m:n$ relationship $R_{12}$. $E_{1}$ and $E_{3}$ are connected by a $1 : n$ ($1$ on the side of $E_{1}$ and $n$ on the side of $E_{3}$) relationship $R_{13}$. $E_{1}$ has two-singled attributes $a_{11}$ and $a_{12}$ …

Consider the following relation: …