Chapter 6: Transforming Data Models into Database Designs

To represent a 1:1 binary relationship in a relational database design, the key of one table is placed into the second table

True

IN many-to-many relationships in a relational database design, the primary keys of both tables are joined into a composite primary key in the intersection table.

True

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

True

In 1:N relationships, the table on the "many" side is called the child

True

In 1:N relationships, the table on the "one" side is called the parent

True

In a 1:1 relationship, the foreign key is defined as an alternate key to make the DBMS enforce uniqueness

True

In a relational database design, all relationships are expressed by creating a foreign key.

True

In representing a 1:N relationship in a relational database design, the key kof the table representing the parent entity is placed as a foreign key in the table representing the child entity.

True

The first step in the database design process is to create tables and columns from entities and attributes

True

The ideal primary key is short, numeric, and fixed

True

The last step in creating a table is to verify table normalization

True

The values of a surrogate key have no meaning to the users

True

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

True

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

True

Data types are consistent across all DBMS products

False

It is easy to enforce the referential integrity actions for N:M relationships

False

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 is called a cascading insertion

False

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."

False

To represent a 1:N relationship in a relational database design, an intersection table is created

False

The binary constraint MUST COVER indicates that __________. A) A specific binary relationship must be included in a ternary relationships B) A binary relationship includes a set of value combinations that must all occur in a ternary relationship C) A table includes values that must occur in a binary relationship D) A table includes values that must occur in a ternary relationship

B) A binary relationship includes a set of value combinations that must all occur in a ternary relationship

Which of the following is NOT true about representing subtypes in a relational database design? A) One table is created for the supertype and one for each subtype B) All attributes of the supertype are added to the subtype relations C) The key of the supertype is made the key of the subtypes D) An instance of the supertype may be related to one instance eah of several subtypes

B) All attributes of the supertype are added to the subtype relations

In a relational database design, all relationships are expressed by ____. A) Creating a primary key B) Creating a foreign key C) Creating a supertype D) Creating a subtype

B) Creating a foreign key

Which of the following is NOT true of a MUST constraint? A) It may be needed in ternary relationships to enforce special business rules B) It can be expressed directly in a relational model C) It must be enforced by program code D) It requires that one entity be combined with another entity

B) It can be expressed directly in a relational model

When representing a 1:1 relationship in a relational database design, _______. A) The key of each table must be placed as foreign keys into the other B) The key of either table may be placed as a foreign key into the other C) The key of both tables must be the same D) The intersection table gets the key from relations

B) The key of either table may be placed as a foreign key into the other

To represent a one-to-many relationship in a relational database design, ______. A) The key of the child is placed as a foreign key into the parent B) The key of the parent is placed as a foreign key into the child C) An intersection table must be created D) The key of the table on the "many" side is placed in the table on the "one" side

B) The key of the parent is placed as a foreign key into the child

Discriminator attributes can be represented in relational designs.

FALSE

A default value is the value the user enters in to the row the first time the user enters data.

False

A null value is an attribute value that has been set to zero.

False

An entity needs to be examined according to normalization criteria before creating a table from it in the relational database design

False

An intersection table can have additional attributes besides the keys of its parent tables.

False

By default the identifier of the entity becomes the foreign key of the corresponding table

False

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

False

Deciding whether or not an attribute is required is determined during the data modeling phase.

False

IN representing a 1:N relationship in a relational database design, the key of the table representing the entity on the "many" side is placed as a foreign key in the table representing the entity on the "one" side of the relationship.

False

In a 1:N relationship, the term parent refers to the table on the "many" side of the relationship

False

To represent a one-to-many relationship in a relational database design the key of the child table is placed as a foreign key into the other table

False

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

False

When creating a relational database design from E-R diagrams, first create a relation for each relationship

False

When creating a table in the relational database design from an entity in the extended E-R model, the attributes of the entity become the rows of the table.

False

When the key of one table is placed into a second table to represent a relationship, the key is called a relational key in the second table

False

When the parent entity has a surrogate key, the enforcement actions are the same for both parent and child

False

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

False

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

False

Four Uses for ID-Dependent Entities

Representing N:M relationships Representing association relationships Storing multivalued attributes Representing archetype/instance relationships

Like all ID-dependent relationships, the parents of an association table are required

True

One of the important properties of a column is whether or not it can have a NULL value

True

One of the important properties of an attribute is whether or not it is required

True

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

True

To represent an N:M relationship in a relational database design, a table is created between two tables to represent the relationship itself

True

To represent an N:M relationship in a relational database design, an intersection table is created

True

To represent an N:M relationship in a relational database design, in essence it is reduced to two 1:N relationships

True

When child entity is required (M) in a relationship, there needs to always be at least child row for each parent row.

True

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

True

When placing a foreign key for a 1:1 relationship, the key of either table can be used as the foreign key in the other table

True

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 ID-dependent relationship

True

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.

true

A foreign key is a key that does not belong in any table

False

Which of the following is NOT true for an ideal primary key? A) A composite of several long attributes B) numeric C) fixed D) short

A) A composite of several long attributes

The identifier of the entity becomes the ________ of the corresponding table. A)Primary key B) Foreign key C) Supertype D) Subtype

A) Primary key

In many-to-many relationships between strong entities in a relational database design, which of the following is NOT true? A) The intersection table is ID-dependent on one of the parents B) The intersection table is ID-dependent on both of the parents C) The relationships from the intersection table to the parent tables are identifying relationships D) The maximum cardinality to the intersection table is always N

A) The intersection table is ID-dependent on one of the parents

When representing a "one-to-many" relationship in a relational database design, _______. A) The parent is always on the one side of the "one-to-many" relationship B) The child is always on the one side of the "one-to-many" relationship C) Either parent or child can be on the one side of the one-to-many" relationship, and the choice is arbitrary D) Either parent or child can be on the one side of the "one-to-many" relationship, and special criteria indicate which table should be on the one side

A) The parent is always on the one side of the "one-to-many" relationship

When transforming an E-R data model into a relational database design, the key of the parent entity should be placed as part of the primary key into the child entity_______. A) When the child entity is ID-dependent B) When the child entity is non-ID-dependent C) When the child entity has 1:1 relationship with the parent entity D) When the child entity has a 1:N relationship with the parent entity

A) When the child entity is ID-dependent

Each attribute of an entity becomes a(n) __________ of a table. A) Column B) Primary key C) Foreign key D) alternate key

A) column

When transforming an E-R data model into a relational database design, the referential integrity constraints should allow __________________. A) Parent updates to cascade B) Child updates to cascade C) Child deletes to cascade D) Both A and B are correct

A) parent updates to cascade

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 ___________. A) Incremental updates B) Incremental deletes C) Cascading updates D) Cascading deletes

C) Cascading updates

The first step in transforming an extended E-R model into a relational database design is to: A) Create a table for each relationship B) Evaluate the entities against the normalization criteria C) Create a table for each entity D) Remove any recursive relationships

C) Create a table for each entity

Which of the following is NOT true about a NULL attribute? A) On insertion, entering the data for that field is optional B) It is an imoportant property of an attribute C) It must have a default value specified D) A primary key can't be NULL

C) It must have a default value specified.

In relational database design, ID-dependent entities are NOT used to _____. A) represent N:M relationships B) handle associative relationships C) Represent relationships where the child identifier does not include the key of the parent D) Handle archetype/instance relationships

C) Represent relationships where the child identifier does not include the key of the parent

A surrogate key should be considered when ________________. A) A relationship is N:M B) A composite key is required C) The key contains a lengthy text field D) The key contains a number

C) The key contains a lengthy text field

In many-to-many relationships in a relational database design, ______ A) The key of the child is placed as a foreign key into the parent B) The key of the parent is placed as a foreign key into the child C) The keys of both tables are placed in a third table D) The keys of both entity tables are placed in each other

C) The keys of both tables are placed in a third table

Which of the following is NOT true about surrogate keys? A) They are identifiers that are supplied by the system, not the users. B) They have no meaning to the users C) They are non-unique within a table D) They can be problematic when combining databases

C) They are non-unique within a table

The binary constraint MUST NOT indicates that __________. A) A specific binary relationship must not be included in a ternary relationship B) A table includes values that must not occur in a binary relationship C) A table inclueds values that must not occur in a ternary relationship D) A binary relationship includes value combinations that must not occur in a ternary relationship

D) A binary relationship includes value combinations that must not occur in a ternary relationship

Many-to-many relationships are relationships are represented by ____. A) Two tables with an M:N relationship B) Two tables with a 1:N relationship C) An intersection table which has M:N relationships with the two tables D) An intersection table which has 1:N relationships with the two tables

D) An intersection table which has 1:N relationships with the two tables

A referential integrity constraint policy that guarantees that a row in a parent table always has a required entry in a child table ___________. A) is known as a minimum cardinality enforcement action B) Needs to be documented by the database development team C) Is enforced in most DBMS products D) Both A and B are correct

D) Both A and B are correct

For the M-O (parent mandatory, child optional) case, what action(s) should be taken to ensure minimum cardinality is maintained? A) Define referential integrity constraint from child to parent B) Make foreign key NOT NULL C) Will require trigger or other application code D) Both A and B are correct

D) Both A and B are correct

In a supertype-subtype structure, discriminator attributes ____________. A) Are easily represented in a relational design B) Cannot be represented in a relational design C) Require application logic to determine which subtypes correspond to a specific supertype instance D) Both B and C are correct

D) Both B and C are correct

Which of the following is NOT true about N:M recursive relationships? A) Both foreign keys in the intersection table refer to the same table B) Since it is a recursive relationship, an intersection table is not needed. C) The foreign keys in the intersection table can't refer to the same attribute in the parent table. D) Both B and C are correct

D) Both B and C are correct

A referential integrity constraint policy that insures that all rows containing a 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 ______________. A) Incremental updates B) Incremental deletes C) Cascading updates D) Cascading deletes

D) Cascading deletes

Which of the following is NOT true of recursive relationships? A) When the recursive relationship is M:N, an intersection table is created. B) The rows of a single table can play two different roles. C) Recursive relationships can be 1:1, 1:N, or M:N relationships D) When the relationship is 1:N, a new table must be defined to represent the relationship

D) When the relationship is 1:N, a new table must be defined to represent the relationship

Which of the following is NOT a step in the database design process? A) Create tables and columns from entities and attributes B) Select primary keys C) Represent relationships D) Create constraints and triggers

D. Create constraints and triggers

A data constraint is a limitation on data values

True

A key of an intersection table is always the combination of the keys of both parents

True

A referential integrity constraint policy that insures that all rows containing a 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

True

A surrogate key is a unique, system-supplied identifier often used as the primary key of a table

True

A surrogate key is appropriate when the primary key of a table contains a lengthy text field

True

A surrogate key should be considered when the key contains a lengthy text field

True

All identifying relationships are 1:N.

True

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

True

An intersection table is always ID-dependent on both of its parent tables

True

Association tables sometimes connect more that two entities

True

Cascading deletions are generally not used with relationships between strong entities

True

Each entity in the extended E-R model is represented as a table in the relational database design

True