ER Model GATE CS PYQ Quiz (original) (raw)

Given the basic ER and relational models, which of the following is INCORRECT?

• An attribute of an entity can have more than one value
• An attribute of an entity can be composite
• In a row of a relational table, an attribute can have more than one value
• In a row of a relational table, an attribute can have exactly one value or a NULL value

Consider the following ER diagram.

The minimum number of tables needed to represent M, N, P, R1, R2 is

Consider the data given in above question. Which of the following is a correct attribute set for one of the tables for the correct answer to the above question?

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

• Diamonds with double/bold border
• Rectangles with double/bold border
• Ovals with double/bold border
• Ovals that contain underlined identifiers

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 E1 is greater that the cardinality of E2. Which one of the following is true about R?

• Every entity in E1 is associated with exactly one entity in E2.
• Some entity in E1 is associated with more than one entity in E2.
• Every entity in E2 is associated with exactly one entity in E1.
• Every entity in E2 is associated with at most one entity in E1.

Let E1 and E2 be two entities in an E/R diagram with simple single-valued attributes. R1 and R2 are two relationships between E1 and E2, where R1 is one-to-many and R2 is many-to-many. R1 and R2 do not have any attributes of their own. What is the minimum number of tables required to represent this situation in the relational model?

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?

• S1 is true and S2 is false
• S1 is false and S2 is true

Consider an Entity-Relationship (ER) model in which entity sets E1 and E2 are connected by an m : n relationship R12, E1 and E3 are connected by a 1 : n (1 on the side of E1 and n on the side of E3) relationship R13.

E1 has two single-valued attributes a11 and a12 of which a11 is the key attribute. E2 has two single-valued attributes a21 and a22 is the key attribute. E3 has two single-valued attributes a31 and a32 of which a31 is the key attribute. The relationships do not have any attributes.

If a relational model is derived from the above ER model, then the minimum number of relations that would be generated if all the relations are in 3NF is ___________.

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 of the following conditions, can the relational table for R be merged with that of A?

(A) Relation R is one-to-many and the participation of A in R is total.

(B) Relation R is one-to-many and the participation of A in R is partial.

(C) Relation R is many-to-one and the participation of A in R is total.

(D) Relation R is many-to-one and the participation of A in R is partial.

Let S be the specification: "Instructors teach courses. Students register for courses. Courses are allocated classrooms. Instructors guide students." Which one of the following ER diagrams CORRECTLY represents S?

There are 11 questions to complete.

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