Relational Model

$$ \text { In the context of DBMS, consider the two sets } \mathbf{T} \text { and } \mathbf{S} \text { given below. } $$ $$ \begin{array}{ll}\,\,\,\,\, \text { T } &\,\,\,\,\, \text { S } \\ \text { I: } \text { Logical...

Consider a relational database schema with two relations $R(P, Q)$ and $S(X, Y)$. Let $E=\{\langle u\rangle \mid \exists v \exists w\langle u, v\rangle \in R \wedge\langle v, w\rangle \in S\}$ be a tuple relational calcu...

Consider two relations describing teams and players in a sports league: $\bullet$ teams(tid, tname): tid, tname are team-id and team-name, respectively. $\bullet$ players(pid, pname, tid): pid, pname, and tid denote play...

Consider the following two relations, R(A, B) and S(A, C) : R A B 10 20 20 30 30 40 30 50 50 95 S A C 10 90 30 45 40 80 The total number of tuples obtained by evaluating the following expression $$ \sigma_{B is _________

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

The relation schema, Person ($\underline{\text{pid}}$, $city$), describes the city of residence for every person uniquely identified by $pid$. The following relational algebra operators are available: selection, projecti...

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

Consider the following three relations in a relational database. Employee ( $$\underline {eld} $$ , Name), Brand ( $$\underline {bld} $$ , bName), Own ( $$\underline {eld} $$ , $$\underline {bld} $$) Which of the followi...

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...

Which one of the following is used to represent the supporting many-one relationships of a weak entity set in an entity-relationship diagram?

In an Entity-Relationship $$(ER)$$ model, suppose $$R$$ is a many-to-one relationship from entity set $$E1$$ to entity set $$E2.$$ Assume that $$E1$$ and $$E2$$ participate totally in $$R$$ and that the cardinality of $$...

Consider the relations $$r(A, B)$$ and $$s(B, C),$$ where $$s.B$$ is a primary key and $$r.B$$ is a foreign key referencing $$s.B.$$ Consider the query $$Q:$$ $$\,\,\,\,\,\,\,\,\,$$ $$r$$ $$\,\,\,\,$$ $$\bowtie$$ $$\,\,\...

Consider two relations $${R_1}\left( {A,B} \right)$$ with the tuples $$(1,5), (3,7)$$ and $${R_2}\left( {A,C} \right) = \left( {1,7} \right),\left( {4,9} \right).$$ Assume that $$R(A,B,C)$$ is the full natural outer join...

Consider the relational schema given below, where eId of the relation dependent is a foreign key referring to empId of the relation employee . Assume that every employee has at least one associated dependent in the depen...

Consider the following relational schema. Students( rollno: integer, sname: string) Courses( courseno: integer, cname: string) Registration( rollno: integer, courseno: integer, percent: real) Which of the following queri...

Consider the following relations A, B and C: A ID Name Age 12 Arun 60 15 Shreya 24 99 Rohit 11 B ID Name Age 15 Shreya 24 25 Hari 40 98 Rohit 20 99 Rohit 11 C ID Phone Area 10 2200 02 99 2100 01 How many tuples does the...

Suppose R 1 ( A, B) and R 2 ( C, D) are two relation schemas. Let r 1 and r 2 be the corresponding relation instances. B is a foreign key that refers to C in R 2 . If data in r 1 and r 2 satisfy referential integrity con...

Consider the following relations A, B and C: A ID Name Age 12 Arun 60 15 Shreya 24 99 Rohit 11 B ID Name Age 15 Shreya 24 25 Hari 40 98 Rohit 20 99 Rohit 11 C ID Phone Area 10 2200 02 99 2100 01 How many tuples does the...

The following functional dependencies hold for relations R(A, B, C) and S(B, D, E): $$$\eqalign{ & B \to A \cr & A \to C \cr} $$$ The relation R contains 200 tuples and the relation S contains 100 tuples. What is the max...

Let R and S be relational schemes such that R = { a, b, c } and S = { c }. Now consider the following queries on the database: I. $$\pi_{R-S}(r) - \pi_{R-S} \left (\pi_{R-S} (r) \times s - \pi_{R-S,S}(r)\right )$$ II. $$...

Which of the following tuple relational calculus expression(s) is/are equivalent to $$\forall t \in r \left(P\left(t\right)\right)$$? I. $$\neg \exists t \in r \left(P\left(t\right)\right)$$ II. $$\exists t \notin r \lef...

Consider The Following Relational Scheme Student ( school-id, sch-roll-no , sname, saddress) School ( school-id , sch-name, sch-address, sch-phone) Enrolment ( school-id, sch-roll-no, erollno, examname) ExamResult ( Erol...

Let R and S be two relations with the following schema R ( P , Q , R1, R2, R3) S ( P , Q , S1, S2) Where {P, Q} is the key for both schemas. Which of the following queries are equivalent? I. $$\Pi_P \left(R \bowtie S\rig...

Consider the relation employee(name, sex, supervisorName) with name as the key, supervisorName gives the name of the supervisor of the employee under consideration. What does the following Tuple Relational Calculus query...

Information about a collection of students is given by the relation studInfo(studId, name, sex) . The relation enroll(studId, courseId) gives which student has enrolled for (or taken) what course(s). Assume that every co...

Which of the following relational query languages have the same expressive power? I) Relational algebra II) Tuple relational calculus restricted to safe expressions III) Domain relational calculus restricted to safe expr...

Consider the relations r 1 (P, Q, R) and r 2 (R, S, T) with primary keys P and R respectively. The relation r 1 contains 2000 tuples and r 2 contains 2500 tuples. The maximum size of the join $${r_1} \Join {r_2}$$ is

Let $${E_1}$$ and $${E_2}$$ be two entities in an E-R diagram with simple single-valued attributes, $${E_1}$$ and $${E_2}$$ are two relationships between $${E_1}$$ and $${E_2}$$, Where $${E_1}$$ is one-to-many and $${E_2...

Let R 1 ( A, B, C) and R 2 ( D, E) be two relation schema, where the primary keys are shown underlined, and let C be a foreign key in R 1 referring to R 2 . Suppose there is no violation of the above referential integrit...

Consider the following relation schema pertaining to a students database: Students ( rollno , name, address) Enroll( rollno,courseno , coursename) Where the primary keys are shown underlined. The number of tuples in the...

Consider the following SQL query: Select distinct a 1 , a 2 , ..., a n From r 1 , r 2 , ..., r m Where P; For an arbitrary predicate P, this query is equivalent to which of the following relational algebra expressions?

With regard to the expressive power of the formal relational query languages, which of the following statements is true?

Which of the following relational calculus expressions is not safe?

Given the relations employee (name, salary, deptno) , and department (deptno, deptname, address) Which of the following queries cannot be expressed using the basic relational algebra operations $$\left(\sigma, \pi,\times...

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

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

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 $$S$$ (a) Insert into $$R$$ (b)...

A library relational database system uses the following schema USERS (User #, User Name, Home Town) BOOKS (Books # Book Title, Author Name) ISSUED (Book #, User #, Date) Explain in one English sentence, what each of the...

Give a relational algebra expression using only the minimum number of operators from $$\left( { \cup ,\, - } \right)$$ which is equivalent to $$R \cap S$$.