Chapter 2 Quiz

a candidate to be the primary key

A candidate key is ________. A) a combination of two or more attributes B) is always automatically generated by the DBMS C) None of these D) a candidate to be the primary key E) never a primary key

True

A double arrow notation, A →→ B, is used to indicate a multivalued dependency.

The available candidate keys would be prone to typographical errors.

A surrogate key may be appropriate under which of the following circumstances? A) The relation only has one attribute. B) The available candidate keys have little meaning to the users. C) The primary key is not unique. D) The available candidate keys would be prone to typographical errors. E) The primary key is numeric

False

Any table that meets the definition of a relation is said to be in second normal form.

False

Candidate keys may or may not be unique.

True

Ensuring that every value of a foreign key matches a value of the corresponding primary key is an example of a referential integrity constraint.

True

Given the functional dependency for the attributes of ENTITY1, X → (A, B, C), X is a candidate key for the relation ENTITY1 (A, B, C, X).

False

In the normalization process, if you find a candidate key that is not a primary key, then you have determined that the relation needs to be broken into two or more other relations.

True

In the normalization process, if you find that every determinant in a relation is a candidate key, then you have determined that the relation is well formed.

False

In the normalization process, it is not necessary to identify all the functional dependencies in a relation.

False

In the relational model, each row of a table contains data that represents an attribute of the entity.

False

Microsoft Access forms can only contain data from one table.

True

Null values can cause problems because they are ambiguous.

False

Since surrogate keys are used to uniquely identify rows, their values are normally displayed prominently on all forms and reports for the users to see.

True

Surrogate key values have no meaning to the users.

True

The first step of the normalization process is to identify all the candidate keys of a relation.

True

The primary key is used both to identify unique rows in a relation and to represent rows in relationships.

False

The use of surrogate keys usually complicates application programming since most DBMS products require the application program to generate surrogate key values.

True

To be considered a composite key, a key must contain at least two attributes.

True

To create a well-formed relation through normalization, every determinant must be a candidate key.

(BuildingName, RoomNumber) → (Capacity, Department)

Which of the following functional dependency diagrams accurately represents the following situation: • A campus has many buildings.• Each building has a unique name. • Each building has many rooms. • All rooms in any given building are numbered sequentially starting at "101." • Each room has a certain capacity, although many rooms in the same building or different buildings may have the same capacity. • Each room is assigned to a single department. • A department may have many rooms in one or more buildings, each with the same or different capacities. A) RoomNumber → (BuildingName, Department, Capacity) B) (BuildingName, Capacity) → (Department, RoomNumber) C) (BuildingName, RoomNumber) → (Capacity, Department) D) BuildingName → (RoomNumber, Capacity, Department) E) (Department, Capacity) → (BuildingName, RoomNumber)

Null values cannot be avoided.

Which of the following is not true about null values? A) Null values cannot be avoided. B) A null value can mean that the value is unknown. C) A null value can mean that the value is known to be blank. D) A null value can mean that no value for the field is appropriate. E) A null value is ambiguous.

Row

Which of the following terms is synonymous with "tuple"? A) Row B) Attribute C) Relation D) Field E) Table

true

true-breeding

False

A key must be unique.

composite key

A key that contains more than one attribute is called a(n) ________. A) multi-key B) composite key C) candidate key D) n-key E) complex key

a candidate key

A primary key is ________. A) a candidate key B) used to represent columns in relationships C) always automatically generated by the DBMS D) comprised of exactly one attribute E) not required to be unique

key

A(n) ________ is one or more columns of a relation that is used to identify a row. A) key B) attribute C) Record D) database

modification problems

Although Microsoft Access is a personal database, the database tables in Access are still subject to ________ if they are not well-formed.

true

Every cell in a relation can hold only a single value.

The problem with allowing null values in a table is that the null value is open to three different interpretations. First, a null value in a field may mean that no value is appropriate for the field for the given record. Second, a null value may mean that the value of that field is known to be blank for the given record. Third, a null value may mean that the value of that field is not known for the given record.

Explain the possible interpretations of a null value.

The terms relation, tuple, and attribute are used primarily by database theoreticians. These terms are synonymous with the terms table, row, and column, respectively, in regards to a relational database. They are also equivalent to the terms file, record, and field, which tend to be used by many traditional data processing professionals.

Explain the terms relation, tuple, and attribute.

MedicineName is a determinant.

Given the below functional dependency,MedicineCode → (MedicineName, ShelfLife, Manufacturer, Dosage)which of the following statements is not known to be true? A) MedicineCode is a candidate key of the relation MEDICINE (MedicineName, ShelfLife, Manufacturer, Dosage). B) MedicineCode is a determinant. C) MedicineName is a determinant. D) ShelfLife is functionally dependent on MedicineCode. E) Manufacturer is functionally dependent on MedicineCode.

True

If the condition exists such that knowing the value of attribute X determines the value of attribute Y, then attribute Y is functionally dependent on attribute X.

identity Seed

In SQL Server, the starting value of a surrogate key is called the ________. A) identity Start B) identity Seed C) identity D) identity increment E) identity property

False

Normalization is the process of removing all functional dependencies from a relation.

They are meaningful to the users.

Which of the following is not true of surrogate keys? A) They are unique. B) They are usually hidden on forms and reports. C) They are numeric. D) They are meaningful to the users. E) They are usually generated by the DBMS.

Both It may be unique and It may be non-unique

Which of the following is true about a key? A) It may be non-unique. B) It may be unique. C) It can only identify one row. D) Both It may be unique and It may be non-unique E) None of these

Table

Which of the following terms is synonymous with "relation"? A) Tuple B) Record C) Row D) Table E) Attribute

False

While the relational model for databases appears to hold much promise, few commercial databases have implemented it.

Edgar F. Codd

________ was the developer of the relational model for databases.