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C175 Data Management Foundations > Lesson 3 > Flashcards

Lesson 3 Flashcards

1
Q

Domain

A

In data modeling, the construct used to organize and describe an attribute’s set of possible values.

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2
Q

Key

A

One or more attributes that determine other attributes.

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3
Q

What are the types of keys?

A
  • Superkey
  • Candidate key
  • Primary key
  • Secondary key
  • Foreign key
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4
Q

Primary key

A
  1. In the relational model, an identifier composed of one or more attributes that uniquely identifies a row.

candidate key is selected as a unique entity identifier.

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5
Q

Determination

The role of a key

A
  1. In a database table, ‘B determines A’ means that knowing the value of [attribute B] allows you to find the value of [attribute A].
  2. If [B] is a key, this relationship is special: Each value of [B] uniquely identifies a single record, and thus, a single value of [A].
  3. This ensures that no two rows have the same value for [B].”
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6
Q

Functional dependence

A

Within a relation R:

  1. An [attribute A] is functionally dependent on an [attribute B] if and only if
  2. A given value of [attribute B] determines exactly one value of [attribute A].
  3. The “relationship A is dependent on B” is equivalent to “B determines A,” and is written as B-> A.
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7
Q

Determinant

A

Any attribute in a specific row whose value directly determines other values in that row

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8
Q

Dependent

A

An attribute whose value is determined by another attribute.

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9
Q

Full functional dependence

A

A condition in which an attribute is functionally dependent on a composite key but not on any subset of the key.

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10
Q

Composite key

A

A multiple-attribute key

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11
Q

Key attributes

A

The attributes that form a primary key

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12
Q

Superkey

Every candidate key is a superkey, but not every superkey is a candidate key.

A
  1. Any combination of columns(attributes) that uniquely identifies a row in a table.
  2. Think of it like a complete address; it has all the information you need to find a specific location.
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13
Q

Candidate key

A
  1. A candidate key is a minimal superkey.
  2. It means you can’t remove any columns (attributes) from it, but still have it uniquely identify a row.

Like a shortened address, it has just the essential information to find the location.

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14
Q

Entity integrity

A
  1. A property of a relational table.
  2. Guarantees each entity has a unique value in a primary key.
  3. Also that the primary key has no null values.
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15
Q

Null

A
  1. Note that a null is not a blank.
  2. The absence of an attribute value.
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16
Q

Foreign key (FK)

A

An attribute or attributes in one table whose values must match the primary key in another table or whose values must be null.

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17
Q

Referential integrity

A

A condition by which a dependent table’s foreign key must have either a null entry or a matching entry in the related table.

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18
Q

Secondary key

A
  • A key used strictly for data retrieval purposes.
  • For example, customers are not likely to know their customer number (primary key), but the combination of last name, first name, middle initial, and telephone number will probably match the appropriate table row.
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19
Q

What are the 3 types of referential integrity rules?

A
  • Delete
  • Insert
  • Update
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20
Q

Flags

A

Special codes implemented by designers to trigger a:

  1. required response
  2. alert end users to specified conditions
  3. encode values.

Flags may be used to prevent nulls by bringing attention to the absence of a value in a table.

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21
Q

Composite entity

A
  • Designed to transform an M:M relationship into two 1:M relationships.
  • The composite entity’s primary key comprises at least the primary keys of the entities that it connects.
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22
Q

What are the other names that refer to the definition of composite entity?

A
  • Bridge entity
  • Associative entity
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23
Q

Linking table

also known as a junction table or an associative entity

A

Used to implement a many-to-many (M:M) relationship, which is then resolved into two one-to-many (1:M) relationships

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24
Q

Index

A
  • An ordered array of index key values and row ID values (pointers).
  • Indexes are generally used to speed up and facilitate data retrieval.
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25
Q

_____ ____ can also be referred to as a index

A

Index key

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26
Q

Unique index

A

An index in which the index key can have only one associated pointer value (row).

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27
Q

What’s the practical significance of taking the logical view?

A

The logical view serves as a reminder of the simple file concept of data storage.

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28
Q

A table can also be thought as?

A

A persistent representation of a logical relation.

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29
Q

Why is the order of the rows and columns not important to the DBMS?

A
  • DBMSs don’t care about row or column order.
  • They use queries based on names and values.
  • Rearranging them doesn’t change the underlying data in the database.
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30
Q

String data types may not be intended for mathematical manipulation, but can include ___ ?

A

Character sets that can include digits or a numeric string.

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31
Q

A candidate key is a ______ superkey without any _______ attributes.

A

A candidate key is a minimal superkey without any unnecessary attributes.

32
Q

Each table _____ represents an attribute.

A

Column

33
Q

Date attributes contain calendar dates stored in a special format known as the _____ date format.

A

Julian

34
Q

A table is also called a _____ because the relational model’s creator, E. F. Codd, used the two terms as synonyms.

A

Relation

35
Q

In a relational table, each column has a specific range of values known as the ______ domain.

A

Attribute

36
Q

_____ logic, used extensively in mathematics, provides a framework in which an assertion (statement of fact) can be verified as either true or false.

A

Predicate

37
Q

Primary keys are required in relational databases to ensure ___.

A

entity integrity

38
Q

Why is the idea of unique determination irrelevant to how databases function?

A
  1. “Determination” isn’t unique to databases.
  2. It also exists in math and logic, where something is precisely defined or fixed.

For example, in a function, the input determines the output.

39
Q

How many types of attributes can determine functional dependence?

A

Functional dependencies can be determined by a single attribute or a combination of multiple attributes.

40
Q

If the [attribute (B)] is functionally dependent on a [composite key (A)]; but not on any subset of that composite key, the [attribute (B)] is fully __?

A
  1. Functional Dependency: Attribute B is functionally dependent on attribute A if each value of A determines exactly one value of B.
  2. Composite Key: A composite key is a key that consists of two or more attributes.
  3. Full Functional Dependency: A full functional dependency occurs when an attribute (B) is functionally dependent on a composite key (A), but not on any subset of that composite key.
41
Q

When you press the Enter key or the Tab key to move to the next entry without making a prior entry of any kind.

This creates what?

A

A NULL is created

42
Q

When can nulls create problems?

A
  1. Variety of the applications- development, software & it’s sophistication.
  2. When functions such as COUNT, AVERAGE, and SUM are used.
43
Q

In the relational model, _____ are important because they are used to ensure that each row in a table is uniquely identifiable.

A

Keys

44
Q

A _____ is a key that can uniquely identify any row in the table.

A

Superkey

45
Q

A _____ key can be described as a minimal superkey, a superkey without any unnecessary attributes.

A

Candidate

46
Q

A _____ is the primary key of one table that has been placed into another table to create a common attribute.

A

Foreign key

47
Q

A _____ key is defined as a key that is used strictly for data retrieval purposes.

A

Secondary

48
Q

When you define a table’s primary key, the DBMS automatically creates a(n) _____ index on the primary key column(s) you declared.

A

Unique

49
Q

In a relational model, ____ are also used to establish relationships among tables and to ensure the integrity of the data.

A

Keys

50
Q

A primary key is a _____ key selected to uniquely identify all other attribute values in any given row.

A

Candidate

51
Q

A table is also called a relation because the relational model’s creator, E. F. Codd, used the two terms as __________.

A

Synonyms

52
Q

A ______ is perceived as a two-dimensional structure composed of rows and columns.

A

Table

53
Q

The word ______, also known as a dataset in Microsoft Access, is based on the mathematical set theory from which Codd derived his model.

A

Relation

54
Q

Rows are sometimes referred to as __________.

A

Records

55
Q

The CUSTOMER table’s primary key is CUS_CODE. The CUSTOMER primary key column has no null entries, and all entries are unique. This is an example of _____ ______.

A

Entity Integrity

56
Q

Referential integrity dictates what?

A
  1. That the foreign key must contain values that match the primary key, in the related table
  2. Must contain null values.
57
Q

The _____ constraint can be placed on a column to ensure that every row in the table has a value for that column.

A

NOT NULL

58
Q

To avoid nulls, some designers use special codes, known as _____, to indicate the absence of some value.

A

Flags

59
Q

RDBMSs enforce ___ automatically.

A

integrity rules

60
Q

How is a one-to-many (1:M) relationship implemented in a relational database model?

A

By putting the foreign key of the “one” side in the table of the “many” side.

61
Q

When are 1:1 relationships necessary in database design? Provide examples.

A
62
Q

The _____ relationship is the “relational model ideal.”

A

1:M

63
Q

The _____ relationship should be rare in any relational database design.

A

1:1

64
Q

How do you implement a M:N relationship.

A

Implemented by creating a new entity in 1:M relationships with the original entities.

65
Q

Another name for a composite entity is a(n) _____ entity.

A

Bridge

66
Q

The ___ relationship is the relational database norm.

A

1:M

67
Q

____ relationships cannot be implemented as such in the relational model.

A

M:N

Many-to-many

68
Q
  1. If one department chair “a professor”, but can chair only one department.
  2. Also the department can have only one department chair.
  3. The entities PROFESSOR and DEPARTMENT exhibit a ___ relationship
A

1:1

69
Q

One characteristic of generalization hierarchies is that they are implemented as ____ relationships.

A

1:1

70
Q

The proper use of ______ keys is crucial to controlling data redundancy.

A

Foreign

71
Q

Proper data ________ design requires carefully defined and controlled data redundancies to function properly.

A

Warehousing

72
Q

What are the database designers two main options when defining a composite table’s primary key?

A
  1. use the combination of foreign keys or
  2. create a new primary key
73
Q

A(n) _____ is an orderly arrangement used to logically access rows in a table.

A

Index

74
Q

A ______ index is an index in which the index key can have only one pointer value (row) associated with it.

A

Unique

75
Q

An index key can have multiple _______ (a composite index).

A

Attributes

C175 Data Management Foundations (19 decks)

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