GATE CS Databases questions

Which of the following statements about a relation $\mathbf{R}$ in first normal form $\text{(1NF)}$ is/are TRUE?

Consider the following two relations, $R(A, B)$ and $S(A, C)$: …

​The symbol $\rightarrow$ indicates functional dependency in the context of a relational database. Which of the following options is/are TRUE?

​​​​Consider the following read-write schedule $\text{S}$ over three transactions $T_{1}, T_{2}$, and $T_{3}$, where the subscripts in the schedule indicate transaction IDs: $S: r_{1}(z) ; w_{1}(z) ; r_{2}(x) ; r_{3}(y) ; w_{3}(y) ; r_{2}(y) ; w_{2}(x) ; w_{2}(y) ;$ Which of the following transaction schedules is/are conflict equivalent to …

​​​​​Once the $\text{DBMS}$ informs the user that a transaction has been successfully completed, its effect should persist even if the system crashes before all its changes are reflected on disk. This property is called

In the context of owner and weak entity sets in the $\text{ER}$ (Entity-Relationship) data model, which one of the following statements is TRUE?

​​​​​Which of the following file organizations is/are $\text{I/O}$ efficient for the scan operation in $\text{DBMS}$?

​​​​Which of the following statements about the Two Phase Locking ($2 \mathrm{PL}$) protocol is/are TRUE?

​​​​​The relation schema, Person (pid, city), describes the city of residence for every person uniquely identified by pid. The following relational algebra operators are available: selection, projection, cross product, and rename. To find the list of cities where at least $3$ persons reside, using the above operators, the minimum number of cross product …

A functional dependency $F: X \rightarrow Y$ is termed as a useful functional dependency if and only if it satisfies all the following three conditions: $\text{X}$ is not the empty set. $\text{Y}$ is not the empty set. Intersection of $\text{X}$ and $\text{Y}$ is the empty set. For a relation $\text{R}$ with $4$ attributes, the total number of …

Which one of the options given below refers to the degree (or arity) of a relation in relational database systems?

Consider the following table named $\text{Student}$ in a relational database. The primary key of this table is $\text{rollNum}.$ $\text{Student}$ …

Consider a database of fixed-length records, stored as an ordered file. The database has $25,000$ records, with each record being $100$ bytes, of which the primary key occupies $15$ bytes. The data file is block-aligned in that each data record is fully contained within a block. The database is indexed by a primary index file, which is also stored as a …

In a relational data model, which one of the following statements is $\text{TRUE}?$

Consider the following three relations in a relational database. $\text{Employee} (\underline{\text{eId}},\text{Name}), \; \text{Brand}(\underline{\text{bId}},\text{bName}), \; \text{Own}(\underline{\text{eId}},\underline{\text{bId}})$ Which of the following relational algebra expressions return the set of $\textit{elds}$ who own all the brands?

Consider a relation $R (A, B, C, D, E)$ with the following three functional dependencies. $AB \rightarrow C; \; BC \rightarrow D; \; C \rightarrow E;$ The number of superkeys in the relation $R$ is ______________ .

Let $\textit{R}_{i}(z)$ and $\textit{W}_{i}(z)$ denote read and write operations on a data element $z$ by a transaction $\textit{T}_{i},$ respectively. Consider the schedule $\textit{S}$ with four transactions. $S: \; R_{4}(x) R_{2}(x) R_{3}(x)R_{1}(y) W_{1}(y) W_{2}(x) W_{3}(y) R_{4}(y)$ Which one of the following serial schedules is conflict …

Consider the relational database with the following four schemas and their respective instances. Student(sNo, sName, dNo) Dept(dNo, dName) Course(cNo, cName, dNo) Register(sNo, cNo) …

Suppose a database system crashes again while recovering from a previous crash. Assume checkpointing is not done by the database either during the transactions or during recovery. Which of the following statements is/are correct?

A relation $r(A, B)$ in a relational database has $1200$ tuples. The attribute $A$ has integer values ranging from $6$ to $20$, and the attribute $B$ has integer values ranging from $1$ to $20$. Assume that the attributes $A$ and $B$ are independently distributed. The estimated number of tuples in the output of …