Question 1

GENERIC ERD
Observe the GENERIC ER Diagram below:
 
This ER diagram will be used for the following questions citing Generic ER Diagram.
-If in the GENERIC ERD the Symbol 1 is >| and the Symbol2 is ||,then the number of optional columns in the relational schema resulting from mapping the GENERIC ERD is 0.

Accepted Answer

The symbol || represents an optional relationship, not an optional column.

Question 2

The relation resulting from mapping a weak entity (with a 1:M identifying relationship)has a composite primary key that is composed of the partial identifier and a foreign key corresponding to the primary key of the owner entity.

Accepted Answer

This is true according to the standard ER modeling convention for identifying relationships involving weak entities. The composite primary key of the weak entity relation includes the partial identifier inherited from the identifying relationship and a foreign key that references the primary key of the owning entity. This allows the weak entity records to be uniquely identified and linked to their corresponding owner entity records.

Question 3

An entity and its 1:1 unary relationship are mapped as one relation.

Accepted Answer

In a 1:1 unary relationship, an entity is related to itself in a one-to-one manner. This relationship can be represented as a single relation by adding the foreign key of the entity to its own relation. Therefore, the entity and its 1:1 unary relationship can be mapped as one relation.

Question 4

A restriction specifying that no salary entered in the salary column can be higher than $300,000 is an example of a business rule.

Accepted Answer

A restriction specifying a limit on a particular field (salary) is a business rule. It defines a constraint or condition that the data must conform to in order to be considered valid. In this case, the maximum salary limit is $300,000, which is defined as a business rule for the salary column.

Question 5

GENERIC ERD
Observe the GENERIC ER Diagram below:
 
This ER diagram will be used for the following questions citing Generic ER Diagram.
-If in the GENERIC ERD the Symbol 1 is >| and the Symbol2 is 0|,then the number of columns in the relational schema resulting from mapping the GENERIC ERD is 5.

Accepted Answer

Based on the mapping rules for ERD symbols, >| represents a one-to-many relationship where the "one" side is mandatory and the "many" side is optional. 0| represents a zero-to-many relationship where the "zero" side is optional and the "many" side is optional. When mapping these symbols to a relational schema, it results in 5 columns, which are the foreign key column(s) from the "many" side and the primary key column(s) from the "one" side. Therefore, the statement is true.

Question 6

For each employee middle initial is optional is an example of an implicit database constraint.

Accepted Answer

The answer of For each employee middle initial is optional...

Question 7

GENERIC ERD
Observe the GENERIC ER Diagram below:
 
This ER diagram will be used for the following questions citing Generic ER Diagram.
-If in the GENERIC ERD the Symbol 1 is >| and the Symbol2 is 0|,then the number of optional columns in the relational schema resulting from mapping the GENERIC ERD is 0.

Accepted Answer

In an Entity-Relationship Diagram (ERD), the symbols >| and 0| represent cardinality constraints. The >| symbol typically denotes a "many" side of a relationship where participation is mandatory, while the 0| symbol indicates a "many" side where participation is optional. When mapping to a relational schema, an optional relationship (indicated by 0|) would result in optional columns (allowing NULL values) in the corresponding table to accommodate instances where the relationship does not exist. Therefore, the presence of a 0| symbol implies that there could be optional columns in the resulting relational schema, contradicting the statement that the number of optional columns is 0.

Question 8

ZYX COMPANY
Observe the ER diagram for the ZYX COMPANY:
 
This ER diagram will be used for the following questions citing ZYX Company ER Diagram.
-During mapping of the ZYX Company ERD into a relational schema,attribute EmpID from the ZYX Company ER diagram will be mapped as a column of the relation EMPLOYEE.

Accepted Answer

The attribute EmpID from the ZYX Company ER diagram will be mapped as a column of the relation EMPLOYEE during mapping of the ERD into a relational schema.

Question 9

Every attribute appears only once in an ER diagram

Accepted Answer

In an ER diagram, a particular attribute can only appear once to avoid redundancy and ensure data accuracy.

Question 10

When an entity has multiple unique attributes,each one of them is mapped as a primary key of the resulting relation.

Accepted Answer

Each entity should have only one primary key attribute that uniquely identifies the entity, and all other attributes should be mapped as non-primary key attributes in the resulting relation. Having multiple primary key attributes for a single entity violates database normalization rules and can lead to data redundancy and inconsistencies.

Question 11

GENERIC ERD
Observe the GENERIC ER Diagram below:
 
This ER diagram will be used for the following questions citing Generic ER Diagram.
-If in the GENERIC ERD the Symbol 1 is >| and the Symbol2 is ||,then the number of relations in the relational schema resulting from mapping the GENERIC ERD is 2.

Accepted Answer

The Symbol 1 (>|) represents a one-to-many relationship, while the Symbol 2 (||) represents a many-to-many relationship. Both of these relationships will result in a separate relation in the relational schema, so the total number of relations would be 2.

Question 12

GENERIC ERD
Observe the GENERIC ER Diagram below:
 
This ER diagram will be used for the following questions citing Generic ER Diagram.
-If in the GENERIC ERD the Symbol 1 is >| and the Symbol2 is 0<,then the number of optional columns in the relational schema resulting from mapping the GENERIC ERD is 0.

Accepted Answer

The symbols >| and 0< indicate a mandatory one-to-many relationship on one end and an optional many-to-one relationship on the other end respectively. In this case, there are no optional columns resulting from the mapping of this relationship to a relational schema.

Question 13

An entity and its 1:M unary relationship are mapped as one relation.

Accepted Answer

In a 1:M unary relationship, the entity on the "one" side is connected to multiple instances of itself on the "many" side. This can be represented by adding a foreign key in the "many" side that references the primary key of the "one" side. Since this relationship can be represented within a single relation, the entity and its 1:M unary relationship are mapped as one relation.

Question 14

A bridge relation is a result of mapping an M:N relationship.

Accepted Answer

A bridge relation is used to resolve an M:N relationship by creating a new entity that has relationships with the two original entities, allowing for more efficient and organized data management.

Question 15

GENERIC ERD
Observe the GENERIC ER Diagram below:
 
This ER diagram will be used for the following questions citing Generic ER Diagram.
-If in the GENERIC ERD the Symbol 1 is >| and the Symbol2 is ||,then the number of columns in the relational schema resulting from mapping the GENERIC ERD is 5.

Accepted Answer

The Symbol1 >| indicates a one-to-many relationship, while the Symbol2 || indicates a one-to-one relationship. When mapping these relationships to a relational schema, the one-to-many relationship would result in a foreign key being added to the table with the many end, while the one-to-one relationship would result in the attribute being added directly to the table. This would result in a total of 5 columns in the relational schema.

Question 16

Each weak entity has one owner entity.

Accepted Answer

The answer of Each weak entity has one owner entity....

Question 17

GENERIC ERD
Observe the GENERIC ER Diagram below:
 
This ER diagram will be used for the following questions citing Generic ER Diagram.
-If in the GENERIC ERD the Symbol 1 is >| and the Symbol2 is 0|,then the number of relations in the relational schema resulting from mapping the GENERIC ERD is 2.

Accepted Answer

The symbols >| and 0| represent maximum and minimum cardinality, respectively. If Symbol 1 (>|) is used, it means that there is a mandatory one-to-many relationship between two entities. If Symbol 2 (0|) is used, it means that there is an optional one-to-many relationship between two entities. Each of these symbols will result in a separate relation in the resulting relational schema, hence the total number of relations will be 2.

Question 18

An entity and its M:N unary relationship are mapped as one relation.

Accepted Answer

In database design, an M:N unary relationship (many-to-many relationship with itself) requires at least two tables to be properly represented: one for the entity and another for the relationship, to store pairs of entity identifiers that are related.

Question 19

GENERIC ERD
Observe the GENERIC ER Diagram below:
 
This ER diagram will be used for the following questions citing Generic ER Diagram.
-If in the GENERIC ERD the Symbol 1 is >| and the Symbol2 is 0<,then the number of relations in the relational schema resulting from mapping the GENERIC ERD is 2.

Accepted Answer

The number of relations resulting from mapping an ERD to a relational schema depends on the entities and relationships in the ERD, not just the cardinality symbols.

Question 20

GENERIC ERD
Observe the GENERIC ER Diagram below:
 
This ER diagram will be used for the following questions citing Generic ER Diagram.
-If in the GENERIC ERD the Symbol 1 is >| and the Symbol2 is 0<,then the number of columns in the relational schema resulting from mapping the GENERIC ERD is 5.

Accepted Answer

The symbols >| and 0< indicate a one-to-many relationship, which means that Symbol1 will be mapped to a foreign key in the many-side (containing a single bar) table and Symbol2 will be mapped to a primary key in the one-side (containing a double bar) table. This mapping will result in the creation of at least six columns in the resulting relational schema: the primary key column in the one-side table, the foreign key column in the many-side table, and at least four other columns to represent the attributes of each entity. Therefore, the correct answer is B, as the number of columns in the schema will be at least six.

Quiz 3: Relational Database Modeling

The relation resulting from mapping a weak entity (with a 1:M identifying relationship)has a composite primary key that is composed of the partial identifier and a foreign key corresponding to the primary key of the owner entity.

An entity and its 1:1 unary relationship are mapped as one relation.

A restriction specifying that no salary entered in the salary column can be higher than $300,000 is an example of a business rule.

GENERIC ERD Observe the GENERIC ER Diagram below: This ER diagram will be used for the following questions citing Generic ER Diagram. -If in the GENERIC ERD the Symbol 1 is >| and the Symbol2 is 0|,then the number of columns in the relational schema resulting from mapping the GENERIC ERD is 5.

For each employee middle initial is optional is an example of an implicit database constraint.

Every attribute appears only once in an ER diagram

When an entity has multiple unique attributes,each one of them is mapped as a primary key of the resulting relation.

GENERIC ERD Observe the GENERIC ER Diagram below: This ER diagram will be used for the following questions citing Generic ER Diagram. -If in the GENERIC ERD the Symbol 1 is >| and the Symbol2 is ||,then the number of relations in the relational schema resulting from mapping the GENERIC ERD is 2.

An entity and its 1:M unary relationship are mapped as one relation.

A bridge relation is a result of mapping an M:N relationship.

GENERIC ERD Observe the GENERIC ER Diagram below: This ER diagram will be used for the following questions citing Generic ER Diagram. -If in the GENERIC ERD the Symbol 1 is >| and the Symbol2 is ||,then the number of columns in the relational schema resulting from mapping the GENERIC ERD is 5.

Each weak entity has one owner entity.

GENERIC ERD Observe the GENERIC ER Diagram below: This ER diagram will be used for the following questions citing Generic ER Diagram. -If in the GENERIC ERD the Symbol 1 is >| and the Symbol2 is 0|,then the number of relations in the relational schema resulting from mapping the GENERIC ERD is 2.

An entity and its M:N unary relationship are mapped as one relation.

GENERIC ERD Observe the GENERIC ER Diagram below: This ER diagram will be used for the following questions citing Generic ER Diagram. -If in the GENERIC ERD the Symbol 1 is >| and the Symbol2 is 0<,then the number of relations in the relational schema resulting from mapping the GENERIC ERD is 2.

GENERIC ERD Observe the GENERIC ER Diagram below: This ER diagram will be used for the following questions citing Generic ER Diagram. -If in the GENERIC ERD the Symbol 1 is >| and the Symbol2 is 0<,then the number of columns in the relational schema resulting from mapping the GENERIC ERD is 5.