CS 3410 - Intro to Database Systems

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

True

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

False

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

True

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

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

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

False

The ideal primary key is short, numeric, and fixed.

True

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

True

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

True

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

True

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

True

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

True

Whether or not an attribute is required is determined during the database modeling phase.

False

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

False

Data types are consistent across all DBMS products.

False

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

False

A data constraint is a limitation on data values.

True

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

True

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

True

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

False

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

True

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

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

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

True

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

False

In a 1:N relationship, the table on the 'one' side is called the parent.

True

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

True

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

False

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

False

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

True

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 N:M relationship in a relational database design, a table is created 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

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

True

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

True

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

True

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

False

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

True

An association table sometimes connects more than two entities.

True

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

True

All identifying relationships are 1:N.

True

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.

True

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

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.

True

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

False

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.

True

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

False

Discriminator attributes can be represented in relational designs.

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

True

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

True

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.

True

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 insertions.

False

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.

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

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

True

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

False

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

True

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

False

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

True

It is easy to enforce the referential integrity actions for M-M relationships.

False

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

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

Each attribute of an entity becomes a(n) of a table.

A) column

B) primary key

C) foreign key

D) alternate key

A) column

The identifier of the entity becomes the of the corresponding table.

A) primary key

B) foreign key

C) supertype

D) subtype

A) primary key

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

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

Which of the following is not true about surrogate keys?