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45 Cards in this Set

  • Front
  • Back

The price paid for increased performance through Denormalization is a larger amount of _______.

REDUNDANCY


(from the quiz)

____________ is a process to help reduce the likelihood of data anomalies.

NORMALIZATION


(from the quiz)

Any attribute that is at least part of a key is known as a _________.

PRIME ATTRIBUTE


(from the quiz)

A dependency based on only a part of a composite primary key is called a ______.

PARTIAL DEPENDENCY


(from the quiz)

Dependencies can be identified with the help of a dependency _____.

DIAGRAM


(from the quiz)

The problem with transitive dependencies is that they still yield data _____.

ANOMALIES


(from the quiz)

The _____ is central to a discussion of normalization.

CONCEPT OF KEYS


(from the quiz)

All relational tables satisfy the ____ requirements.

1NF


(from the quiz)

Data redundancies occur from _____ of data on every row entry.

DUPLICATION


(from the quiz)

Because a partial dependency can exist only when a table’s primary key is composed of several attributes, a table whose _____ key consists of only a single attribute is automatically in 2NF once it is in 1NF.

PRIMARY


(from the quiz)

Any attribute whose value determines other values within a row is known as a _____.

DETERMINANT


(from the quiz)

An attribute that cannot be further subdivided is said to display


_____.

ATOMICITY


(from the quiz)

_____ refers to the level of detail represented by the values stored in a table’s row.

GRANULARITY


(from the quiz)

In a real-world environment, changing granularity requirements might dictate changes in primary key selection, and those changes might ultimately require the use of _____.

SURROGATE KEYS


(from the quiz)

It becomes difficult to create a suitable _____ key when the related table uses a composite primary key.

FOREIGN


(from the quiz)

When a non-key attribute is the determinant of a key attribute, the table is in 3NF but not in _____.

BCNF


(from the quiz)

In the _____, no row may contain two or more multivalued facts about an entity.

4NF


(from the quiz)

The combination of _____ and ER modeling yields a useful ERD, whose entities may now be translated into appropriate table structures.

NORMALIZATION


(from the quiz)

An ERD is created through a (n) _____ process.

ITERATIVE


(from the quiz)

According to the data-modeling checklist, _____ should be nouns that are familiar to business, should be short and meaningful, and should document abbreviations, synonyms, and aliases for each entity.

ENTITY NAMES


(from the quiz)

The normalization process has these four steps:

1. Each table represents a single subject


2. No data item will be unnecessarily stored in more than one table


3. All nonprime attributes in a table are dependent on the primary key, the entire primary key and nothing but the primary key


4. Each table is void of insert, update or deletion anomalies (ensures integrity and consistency of data)


(from page 195)

1NF

All key attributes are defined, no repeating groups, and all remaining attributes are dependent on the primary key.




You get to 1NF by:


eliminating repeating groups


identifying the primary key


identifying all dependencies

2NF

1NF and no partial dependencies (when you have a multi-valued primary key, and any of the attributes are dependent on only one part of the primary key); can still have transitive dependencies.


You get to 2NF by:


making a new table to eliminate partial dependencies


reassigning corresponding dependent attributes

3NF

2NF and no transitive dependencies (when a dependency exists between two nonprime attributes).


You get to 3NF by:


making new tables to eliminate transitive dependencies


reassigning corresponding dependent attributes

BCNF

Special 3NF where every determinant is a candidate key (a minimal superkey-- an attribute or attributes that uniquely identify each entity in a table--or a key that does not contain a subset of attributes that is itself a superkey)

4NF

3NF and no independent multivalued dependencies.


Follow these two rules:


make sure all attributes are dependent on the primary key, but they must be independent of each other


no row may contain two or more multivalued facts about an entity

atomic attribute

an attribute that cannot be further subdivided to produce meaningful components. For example, a person’s last name attribute cannot be meaningfully subdivided


(from key terms)

atomicity

a property that requires all parts of a transaction to be treated as a single, logical unit of work in which all operations must be completed (committed) to produce a consistent database (taken from atomic transaction property)


(from key terms)

Boyce-Codd normal form (BCNF)

A special type of third normal form (3NF) in which every determinant is a candidate key; a table in BCNF must be in 3NF


(from key terms)

denormalization

A process by which a table is changed from a higher-level normal form to a lower-level normal form, usually to increase processing speed; denormalization potentially yields data anomalies


(from key terms)

dependency diagram

A representation of all data dependencies (primary key, partial, or transitive) within a table


(from key terms)

determinant

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


(from key terms)

first normal form (1NF)

The first stage in the normalization process; it describes a relation depicted in tabular format, with no repeating groups and a primary key identified. All nonkey attributes in the relation are dependent on the primary key.


(from key terms)

fourth normal form (4NF)

A table that is in 3NF and contains no multiple independent sets of multivalued dependencies


(from key terms)

granularity

The level of detail represented by the values stored in a table’s row; data stored at their lowest level of granularity are said to be atomic data


(from key terms)

key/prime attribute

The attributes that form a primary key; an attribute that is part of a key or is the whole key


(from key terms)

nonkey/nonprime attribute

An attribute that is not part of a key


(from key terms)

normalization

A process that assigns attributes to entities so that data redundancies are reduced or eliminated


(from key terms)

partial dependency

In normalization, a condition in which an attribute is dependent on only a portion (subset) of a primary key


(from key terms)

repeating group

In a relation, a characteristic describing a group of multiple entries of the same type for a single key attribute occurrence; for example, a car can have multiple colors for its top, interior, bottom, trim, and so on.


(from key terms)

second normal form (2NF)

The second stage in the normalization process, in which a relation is in 1NF and there are no partial dependencies (dependencies in only part of the primary key)


(from key terms)

surrogate key

A system-assigned primary key, generally numeric and auto-incremented


(from key terms)

third normal form (3NF)

A table is in 3NF when it is in 2NF an no nonkey attribute is functionally dependent on another nonkey attribute; that is, it cannot include transitive dependencies


(from key terms)

transitive dependency

A condition in which an attribute is dependent on another attribute that is not part of the primary key


(from key terms)

data-modeling checklist

Provides a way for the designer to check that the ERD meets a set of minimum requirements.


(from the summary)