Question 1

When transforming supertype/subtype entities into a relational database design,an entity is created for the supertype only.

Accepted Answer

In transforming supertype/subtype entities into a relational database design, entities are created for both the supertype and each subtype, allowing for the representation of both general attributes (in the supertype) and specific attributes (in the subtypes).

Question 2

If the parent is required,then a new child row must be created with a valid foreign key value.

Accepted Answer

If a parent row is required in a foreign key relationship, then a new child row cannot be created unless a valid foreign key value is provided to ensure that the child row is linked to an existing parent row.

Question 3

When creating a table for an ID-dependent entity,both the key of the parent and the key of the entity itself must appear in the table.

Accepted Answer

This is because the ID-dependent entity's identifier is dependent on the parent entity's identifier. So, both the key of the parent entity and the key of the entity itself must be present in the table to establish a relationship between the two entities.

Question 4

All identifying relationships are 1:N.

Accepted Answer

The answer of All identifying relationships are 1:N....

Question 5

Referential integrity constraints should disallow adding a new row to a child table when the foreign key does not match a primary key value in the parent table.

Accepted Answer

This is the purpose of referential integrity constraints - to ensure that foreign keys in child tables reference valid primary keys in parent tables. If a foreign key value does not match any primary key value in the parent table, adding a new row to the child table would violate referential integrity constraints and should be disallowed.

Question 6

When the parent entity is required (M)in a relationship,every row of the child table must have a valid,non-null value of the foreign key.

Accepted Answer

This is because the foreign key in the child table references the primary key of the parent table, thus every row must have a valid reference to a parent entity.

Question 7

When transforming an extended E-R model into a relational database design,recursive relationships are treated fundamentally the same as other HAS-A relationships.

Accepted Answer

Recursive relationships are treated as regular relationships in a relational database design, by creating a separate table for each entity involved in the relationship and establishing foreign key references between them.

Question 8

Association tables sometimes connect more than two entities.

Accepted Answer

Association tables, also known as junction tables or bridge tables, are used to connect two or more entities in a many-to-many relationship. Therefore, they can connect more than two entities.

Question 9

When transforming an ID-dependent E-R data model relationship into a relational database design where the child entity is designed to use a surrogate key,the relationship changes to a weak but not ID-dependent relationship.

Accepted Answer

When a surrogate key is introduced in the child entity, the relationship becomes weak but not ID-dependent because the child entity no longer relies on the parent entity's primary key as a foreign key. Instead, it uses its own surrogate key to establish a relationship with the parent entity.

Question 10

When transforming supertype/subtype entities into a relational database design,the key of the supertype table is placed into the subtype table typically as the key.

Accepted Answer

This is known as the subtype discriminator, which is used to identify which subtype a record belongs to. The key of the supertype table may also be included in the subtype table as a foreign key.

Question 11

When transforming supertype/subtype entities into a relational database design,all of the attributes for the supertype table are placed into the subtype relations.

Accepted Answer

The attributes that are common to all subtypes are placed into the supertype table, and only the unique attributes for each subtype are placed into their respective subtype tables.

Question 12

Discriminator attributes can be represented in relational designs.

Accepted Answer

The answer of Discriminator attributes can be represented in relational...

Question 13

Recursive M:N relationships are represented with an intersection table that shows pairs of related rows from a single table.

Accepted Answer

This statement is true. Recursive M:N relationships are represented with an intersection table that includes pairs of related rows from a single table, linking them together in a many-to-many relationship.

Question 14

To represent an IS-A relationship in a relational database design,the IS-A relationship must be converted into a HAS-A relationship.

Accepted Answer

To represent an IS-A relationship in a relational database design, inheritance can be used to create different tables for each type of object, rather than converting it into a HAS-A relationship.

Question 15

Cascading deletions are generally not used with relationships between strong entities.

Accepted Answer

Cascading deletions are typically used with relationships involving weak entities or associative entities, as they do not have a primary key and their existence depends on the existence of the parent entity. Strong entities have their own primary keys and can exist independently of their relationships with other entities, so cascading deletions are usually not necessary or desirable.

Question 16

An ID-dependent table can be used to represent multivalued attributes.

Accepted Answer

An ID-dependent table is a table that has a primary key that is dependent on another table. This type of table can be used to represent multivalued attributes, where each value is associated with a specific ID. This allows for efficient storage and retrieval of data, and can help to reduce redundancy in the database.

Question 17

Cascading deletions are generally not used with relationships for weak child entities.

Accepted Answer

Cascading deletions are often used with relationships involving weak entities because when a strong entity is deleted, it makes sense to also delete the dependent weak entities to maintain referential integrity. Weak entities do not have a meaningful existence without their parent entity.

Question 18

The design transformation for all IS-A relationships can be summarized by the phrase "place the key of the parent table in the child table."

Accepted Answer

The answer of The design transformation for all IS-A relationships...

Question 19

A referential integrity constraint policy that insures that foreign key values in a table are correctly maintained when there is a change to the primary key value in the parent table is called cascading changes.

Accepted Answer

The answer of A referential integrity constraint policy that insures...

Question 20

A referential integrity constraint policy that insures that all rows containing a particular foreign key value in a table are eliminated from the table when the row containing the corresponding primary key value in a parent table is eliminated from the database is called cascading deletes.

Accepted Answer

Cascading deletes automatically delete dependent rows in child tables when the corresponding row in the parent table is deleted.

Quiz 6: Transforming Data Models Into Database Designs