Recent questions tagged databases

Consider the relation scheme $R = (E, F, G, H, I, J, K, L, M, N)$ and the set of functional dependencies $$\left\{ \{E, F \} \to \{G\}, \{F\} \to \{I, J\}, \{E, H\} \to \...

Consider the following relational database schemes:COURSES (Cno, Name)PRE_REQ(Cno, Pre_Cno)COMPLETED (Student_no, Cno)COURSES gives the number and name of all the availab...

Consider the following database relations containing the attributesBook_idSubject_Category_of_bookName_of_AuthorNationality_of_AuthorWith Book_id as the primary key.What ...

Suppose we have a database consisting of the following three relations.$\text{FREQUENTS (student, parlor)}$ giving the parlors each student visits.$\text{SERVES (parlor, ...

Which of the following query transformations (i.e., replacing the l.h.s. expression by the r.h.s expression) is incorrect? R1 and R2 are relations, C1 and C2 are selectio...

There are five records in a database.$$\begin{array}{|c|c|c|c|} \hline \textbf {Name} & \textbf {Age} & \textbf {Occupation} & \textbf{Category } \\\hline \text{Rama} & ...

Which normal form is considered adequate for normal relational database design?$2NF$$5NF$$4NF$$3NF$

Consider the following transactions with data items $P$ and $Q$ initialized to zero:$${\begin{array}{|c|l|r|c|}\hline \textbf{$T_1$}& \text{read (P);}\\ & \text{read...

Relation $R$ has eight attributes $\text{ABCDEFGH}$. Fields of $R$ contain only atomic values. $F = \{ CH$ $\rightarrow$ $G, A \rightarrow BC, B \rightarrow CFH, E \right...

Consider the following relational schema.Students(rollno: integer, sname: string)Courses(courseno: integer, cname: string)Registration(rollno: integer, courseno: integer,...

Here is para from wiki, about functional dependency in relation dbmsGiven a relation R, a set of attributes X in R is said to functionally determine another set of attrib...

Consider the set of relationsEMP (Employee-no. Dept-no, Employee-name, Salary)DEPT (Dept-no. Dept-name, Location)Write an SQL query to:Find all employees names who work i...

Consider a B-tree with degree $m$, that is, the number of children, $c$, of any internal node (except the root) is such that $m \leq c \leq 2m-1$. Derive the maximum and ...

Which of the following is/are correct?An SQL query automatically eliminates duplicatesAn SQL query will not work if there are no indexes on the relationsSQL permits attri...

Consider the schema $R=(S,T, U, V)$ and the dependencies $S \rightarrow T, T \rightarrow U, U \rightarrow V$ and $V \rightarrow S$. Let $R = (R1\text{ and } R2)$ be a dec...

Which of the following is correct?B-trees are for storing data on disk and B$^+$ trees are for main memory.Range queries are faster on B$^+$ trees.B-trees are for primary...

Let $R = (A, B, C, D, E, F)$ be a relation scheme with the following dependencies $C \rightarrow F, E \rightarrow A, EC \rightarrow D, A \rightarrow B $. Which one of the...

The relational algebra expression equivalent to the following tuple calculus expression:$\left\{t \mid t \in r \land \left(t[A] = 10 \land t[B]=20\right)\right\}$ is$\sig...

Consider the join of a relation $R$ with a relation $S$. If $R$ has $m$ tuples and $S$ has $n$ tuples then the maximum and minimum sizes of the join respectively are$m+n$...

An index is clustered, ifit is on a set of fields that form a candidate keyit is on a set of fields that include the primary keythe data records of the file are organized...

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 \ri...

The relation book (title, price) contains the titles and prices of different books. Assuming that no two books have the same price, what does the following SQL query list...

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.$$\begin{array}{|c|c|} \...

Let $E_1$ and $E_2$ be two entities in an $E/R$ diagram with simple-valued attributes. $R_1$ and $R_2$ are two relationships between $E_1$ and $E_2$, where $R_1$ is one-t...

Let r be a relation instance with schema R = (A, B, C, D). We define $r_1 = \pi_{A, B, C} (R)$ and $r_2=\pi_{A, D} (r)$. Let $s =r_1 \: * \: r_2$ where $*$ denotes natura...

Which one of the following statements about normal forms is $\text{FALSE}?$$\text{BCNF}$ is stricter than $\text{3NF}$Lossless, dependency-preserving decomposition into $...

Which of the following is a key factor for preferring $B^+$-trees to binary search trees for indexing database relations?Database relations have a large number of records...

Consider the following relational schema:$\text{Suppliers}(\underline{\text{sid:integer}},\text{ sname:string, city:string, street:string})$ $\text{Parts}(\underline{\tex...