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http://databases.about.com/library/glossary/blglossary.htm?PM=ss13_databases

<A> DataBase Management Systems / Software:Microsoft AccessDefinition: is an entry-level database that offers a flexible environment for database

developers and users. It makes use of the familiar Microsoft Office interface and allows for

integration with larger-scale enterprise databases such as Microsoft's SQL Server and Oracle.

Cold FusionDefinition: Cold Fusion, a product of Allaire Corporation, is a suite of development tools

designed to facilitate web integration of databases.  It features the Cold Fusion Markup

Language (CFML) which expands upon the features provided by the Hypertext Transfer Protocol

(HTTP) and the Extensible Markup Language (XML).  CFML allows developers to create web-

integrated databases without the complexity inherent in full-scale programming languages

such as Java and C++.

IBM DB2Definition: DB2 is a relational database system developed by IBM Corporation, originally for

use on large mainframe computer systems.  It has since been ported to a variety of platforms

including SunOS, Solaris, Linux, Windows 95/98/NT/2000 and HP-UX.

dBaseDefinition: dBase is a relational database management system first marketed by Ashton-Tate

corporation in the early 1980s.  The data formatting conventions utilized by dBase quickly

became industry standards still in use today.  The dBase Corporation provides support for

legacy and future applications.

Delphi

Definition: Delphi, a product of the Borland Corporation, is a rapid application development

platform that utilizes a visual approach to rapid application development.  Delphi offers

specialized features for database connectivity and application development.

FoxPro

Definition: Microsoft Visual FoxPro is a development environment catering to the needs of

database developers.  Supported platforms include FoxPro, SQL Server and Oracle.

INGRES

Definition: INGRES is a relational database system produced by Computer Associates.  It runs

under a wide variety of operating systems and supports the industry-standard Structured

Query Language.

MySQL

Definition: MySQL is a relational database management system that implements many

industry standards including SQL and ODBC along with C and Perl APIs.  MySQL is made

available under the GNU General Public License (GPL) free of charge and under commercial

license for commercial use.

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Oracle

Definition: Oracle is a powerful relational database management system that offers a large

feature set.  Along with Microsoft SQL Server, Oracle is widely regarded as one of the two most

popular full-featured database systems on the market today.

Online Analytical Processing (OLAP)

Definition: Online Analytical Processing software allows for the real-time analysis of data

stored in a database.  The OLAP server is normally a separate component that contains

specialized algorithms and indexing tools to efficiently process data mining tasks with minimal

impact on database performance.

Online Transaction Processing (OLTP)

Paradox

Definition: Paradox is a relational database management system produced by the Corel

Corporation.

Postgres

Definition: Postgres is an object-oriented relational database management system

(sometimes referred to as an object-relational database).  It began as a research project at the

University of California, Berkely and is available in several free and commercial versions.

Microsoft SQL Server

Definition: Microsoft SQL Server is a powerful relational database management system

catering to high-end users with advanced needs.  Along with Oracle, Microsoft SQL Server is

widely regarded as one of the two main full-featured database systems on the market today.

<B> Database Terminology:Raw Data

Definition: Data consists of a series of facts or statements that may have been collected,

stored, processed and/or manipulated but have not been organized or placed into context. 

When data is organized, it becomes information.  Information can be processed and used to

draw generalized conclusions or knowledge.

Example:  A file listing all of the orders placed through an online service is an example of

data.  If we sort the data by ZIP code and summarize the number of orders that come from

each city, we have created information.  We can create knowledge by taking this information

and making statements such as "Most orders for Widget X come from the northeastern United

States."

Information

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Definition: Information is the processed data ordered in a meaningful way.

Knowledge

Definition: Knowledge consists of generalized conceptual statements that have been

developed through the analysis of information.

Example:  A file listing all of the orders placed through an online service is an example of

data.  If we sort the data by ZIP code and summarize the number of orders that come from

each city, we have created information.  We can create knowledge by taking this information

and making statements such as "Most orders for Widget X come from the northeastern United

States."

DatabaseDefinition: A database is a collection of information organized into interrelated tables of data

and specifications of data objects.

Relation / Table

Definition: A database relation is a predefined row/column format (that defines an entity) for

storing information in a relational database.  Relations are equivalent to tables.

Record / Row

Definition: In a relational database, a row consists of one set of attributes (or one tuple)

corresponding to one instance of the entity that a table schema describes.

Attribute / Field / Column

Definition: Database tables are composed of individual columns corresponding to the

attributes of the object. A single data item related to a database object.  The database schema

associates one or more attributes with each database entity.

Example:  In the following database table, the attributes are <name, ID,

extension>

Name ID Extension

Jim 124 7075

Valeri 128 0853

Bob 192 4214

Domain

Definition: The domain of a database attribute is the set of all allowable values that attribute

may assume.

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Examples: A field for gender may have the domain {male, female, unknown} where those

three values are the only permitted entries in that column.

Tuple

Definition: Tuple is a term from set theory which refers to a collection of one or more

attributes.

Cardinality

Definition: In set theory, cardinality refers to the number of members in the set.  When

specifically applied to database theory, the cardinality of a table refers to the number of rows

(or tuples) contained in a table.

Examples: The table below has cardinality 5:

Name Age SSN Phone Extension

Rob 28 123-45-6789 1242

Amy 34 987-65-4321 9281

Elizabeth 34 111-22-3333 9312

Jim 42 333-22-1111 3214

Mike 29 999-99-9999 2314

Key

Definition: A database key is an attribute utilized to sort and/or identify data in some

manner.  Each table has a primary key which uniquely identifies records.  Foreign keys are

utilized to cross-reference data between relational tables.

Primary Key

Definition: The primary key of a relational table uniquely identifies each record in the table.  It

can either be a normal attribute that is guaranteed to be unique (such as Social Security

Number in a table with no more than one record per person) or it can be generated by the

DBMS (such as a globally unique identifier, or GUID, in Microsoft SQL Server).

Candidate Key

Definition: A candidate key is a combination of attributes that can be uniquely used to identify

a database record.  Each table may have one or more candidate keys.  One of these candidate

keys is selected as the table primary key.

Examples: There are a large number of candidate keys in the sample table

below.  Some of these are <SSN>, <Phone Extension>, <Name, SSN>, and

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<Name, Age, SSN>.  Note that <Age> is not a candidate key in this case

because Amy and Elizabeth share the same age.

Name Age Social Security No (SSN) Phone Extension Department Code

Rob 28 123-45-6789 1242 001

Amy 34 987-65-4321 9281 002

Elizabeth 34 111-22-3333 9312 002

Jim 42 333-22-1111 3214 005

Mike 29 999-99-9999 2314 004

Foreign Key

Definition: A foreign key is a field in a relational table that matches the primary key column

(e.g. department code) of another table (Department). The foreign key can be used to cross-

reference tables.

Index

Definition: An index is a database feature used for locating data quickly within a table. 

Indexes are defined by selecting a set of commonly searched attribute(s) on a table and using

the appropriate platform-specific mechanism to create an index.  

Example:  Personnel information may be store in a Human Resource department's employee

table.  Clerks find that they often search the table for employees by last name but get slow

query responses.  Defining an index on the table consisting of the last name attribute would

speed up these queries. 

Data Mining

Definition: Data mining is the use of automated data analysis techniques to uncover

previously undetected relationships among data items.  Data mining often involves the analysis

of data stored in a data warehouse.  Three of the major data mining techniques are regression,

classification and clustering.

Data Warehouse

Definition: A data warehouse is a centralized database that captures information from various

parts of an organization's business processes.  This information can later be analyzed to

determine predictive relationships through the use of data mining techniques.

Enterprise

Definition: An enterprise is an organization that utilizes computers and applications. In

general use, enterprises refer to businesses/organizations that operate on a large scale.

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Applications that are designed for these organizations are often referred to as enterprise

applications.

Example:  A multinational company that has interconnected computer users located around

the world could be considered an enterprise.  The network operating system that they utilize

can be referred to as an enterprise operating system.  The database that stores their global

sales information is both an enterprise application and an enterprise database.

Entity

Definition: An entity is a single object (e.g. student, course, department, project) about which

data can be stored.  It is the "subject" of a table.  Entities and their interrelationships are

modeled through the use of entity-relationship diagrams.

Definition: An entity is a single object about which data can be stored.  It is the "subject" of a

table.  Entities and their interrelationships are modeled through the use of entity-relationship

diagrams.

Entity-Relationship Diagram

Definition: An entity-relationship diagram is a specialized graphic that illustrates the

interrelationships (e.g. 1 to 1, 1 to N, N to N) between entities in a database.

Also Known As: ER Diagram, E-R Diagram, entity-relationship model

Flat File

Definition: Flat files are data files that contain records with no structured relationships.

Additional knowledge is required to interpret these files such as the file format properties.

Modern database management systems used a more structured approach to file management

(such as one defined by the Structured Query Language) and therefore have more complex

storage arrangements.

Example:  Many database management systems offer the option to export data to comma

delimited file.  This type of file contains no inherent information about the data and

interpretation requires additional knowledge.  For this reason, this type of file can be referred

to as a flat file.

Normalization

Definition: Normalization is the process of structuring relational database schema such that

most ambiguity is removed.  The stages of normalization are referred to as normal forms and

progress from the least restrictive (First Normal Form) through the most restrictive (Fifth

Normal Form).  Generally, most database designers do not attempt to implement anything

higher than Third Normal Form or Boyce-Codd Normal Form.

Boyce-Codd Normal Form (BCNF)

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Definition: A relation is in Boyce-Codd Normal Form (BCNF) if every determinant is a

candidate key.

First Normal Form (1NF)

Definition: A relation is said to be in First Normal Form (1NF) if and only if each attribute of

the relation is atomic.  More simply, to be in 1NF, each column must contain only a single value

and each row must contain the same columns.

Example: The following table is NOT in First Normal Form:

Manager Employees

Jim Susan, Rob, Beth

Mary Alice, John, Asim

Renee Mike

Joe Alan, Tim

Here is an alternative option that IS in 1NF.

Manager Employee

Jim Susan

Jim Rob

Jim Beth

Mary Alice

Mary John

Mary Asim

Renee Mike

Joe Alan

Joe Tim

Second Normal Form (2NF)

Definition: In order to be in Second Normal Form, a relation must first fulfill the requirements

to be in First Normal Form.  Additionally, each nonkey attribute in the relation must be

functionally dependent upon the primary key.

Example: The following relation is in First Normal Form, but not Second Normal

Form:

Order # Customer Contact Person Total

1 Acme Widgets John Doe $134.23

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2 ABC Corporation Fred Flintstone $521.24

3 Acme Widgets John Doe $1042.42

4 Acme Widgets John Doe $928.53

In the table above, the order number serves as the primary key.  Notice that 

the customer and total amount are dependent upon the order number -- this

data is specific to each order.  However, the contact person is dependent upon

the customer.  An alternative way to accomplish this would be to create two

tables:

Customer Contact Person

Acme Widgets John Doe

ABC Corporation Fred Flintstone

 

Order # Customer Total

1 Acme Widgets $134.23

2 ABC Corporation $521.24

3 Acme Widgets $1042.42

4 Acme Widgets $928.53

The creation of two separate tables eliminates the dependency problem experienced in the

previous case.  In the first table, contact person is dependent upon the primary key -- customer

name.  The second table only includes the information unique to each order.  Someone

interested in the contact person for each order could obtain this information by performing a

JOIN operation.

Third Normal Form (3NF)

Definition: In order to be in Third Normal Form, a relation must first fulfill the requirements to

be in Second Normal Form.  Additionally, all attributes that are not dependent upon the

primary key must be eliminated.

Examples: The following table is NOT in Third Normal Form:

Company City State ZIP

Acme Widgets New York NY 10169

ABC Corporation Miami FL 33196

XYZ, Inc. Columbia MD 21046

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In this example, the city and state are dependent upon the ZIP code.  To place this table in

3NF, two separate tables would be created -- one containing the company name and ZIP code

and the other containing city, state, ZIP code pairings.

This may seem overly complex for daily applications and indeed it may be.  Database

designers should always keep in mind the tradeoffs between higher level normal forms and the

resource issues that complexity creates.

Fourth Normal Form (4NF)

Definition: To be in Fourth Normal Form, a relation must first be in Boyce-Codd Normal Form. 

Additionally, a given relation may not contain more than one multivalued attribute.

Examples: The following relation is NOT in Fourth Normal Form:

Ma

nag

er

Ch

ild  

  

Em

plo

yee

JimBet

h

Alic

e

Ma

ry

Bo

bJane

Ma

ry

N

UL

L

Ada

m

Each manager can have more than one child and each manager can supervise more than one

employee.  Therefore, this relation is not in Fourth Normal Form.  The creation of two separate

relations for the Manager/Child and Manager/Employee relationships would put this relation in

Fourth Normal Form.

Functional Dependency

Definition: A functional dependency occurs when one attribute in a relation uniquely

determines another attribute.  This can be written A -> B which would be the same as stating

"B is functionally dependent upon A."

Examples: In a table listing employee characteristics including Social Security Number (SSN)

and name, it can be said that name is functionally dependent upon SSN (or SSN -> name)

because an employee's name can be uniquely determined from their SSN.  However, the

reverse statement (name -> SSN) is not true because more than one employee can have the

same name but different SSNs.

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Lock

Definition: Database management systems utilize locks to provide concurrency control.

Common uses of locks are to ensure that only one user can modify a record at a time and that

data can not be read while it is being modified.  Locking mechanisms can be enforced at the

row, table or page level.

Metadata

Definition: Metadata is literally "data about data."  This term refers to information about data

itself -- perhaps the origin, size, formatting or other characteristics of a data item.  In the

database field, metadata is essential to understanding and interpreting the contents of a data

warehouse.  

Example:  The eXtensible Markup Language (XML) is a metadata format used to define other

data objects.

Replication

Definition: Replication is the process of sharing information between databases (or any other

type of server) to ensure that the content is consistent between systems.  Replication is

normally used to increase the number of database servers available to clients, thereby

reducing the load on each.

Form

Definition: A database form can be used to facilitate database data entry and/or retrieval

operations.  A database developer/administrator usually designs a form which can then be used

by personnel without any specific database skills to perform repetitive tasks.

Examples:  The picture below shows an example form from a Microsoft Access database:

Report

Definition: A database report presents information retrieved from a table or query in a

preformatted, attractive manner.

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Examples: A sample Microsoft Access report is shown below:

Repository

Definition: A repository is a collection of resources that can be accessed to retrieve

information.  Repositories often consist of several databases tied together by a common search

engine.

Transaction

Definition: Transactions are a group of database commands which are to be treated as a

single atomic event.  Transactions are maintained using the two phase commit system.

Two Phase Commit

Definition: Two Phase Commit is the process by which a relational database ensures that

distributed transactions are performed in an orderly manner.  In this system, transactions may

be terminated by either committing them or rolling them back.

Query

Definition: Queries are the primary mechanism for retrieving information from a database and

consist of questions presented to the database in a predefined format.  Many database

management systems use the Structured Query Language (SQL) standard query format.

Structured Query Language (SQL)

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Definition: The structured query language is an industry-standard language used for

manipulation of data in a relational database.  The major SQL commands of interest to

database users are SELECT, INSERT, JOIN and UPDATE.

SELECT

Definition: The SELECT statement in SQL is the primary mechanism for retrieving information

from a relational database.

Examples: Given the following table:

Members

ID LastName Age

1 Smith 25

2 Jones 42

3 Reynolds 36

This SQL statement:

SELECT LastName

FROM Members

WHERE Age>30

Would produce the following results:

LastName

Jones

Reynolds

INSERT

Definition: The INSERT SQL command is used to add records to a table within a database.

Examples: Given the following simple table:

Members

ID Last Name Age

1 Smith 25

2 Jones 42

The following SQL statement could be used to add a new record:

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INSERT INTO Members

VALUES ('3','Reynolds','36')

Which would produce the new table:

ID Last Name Age

1 Smith 25

2 Jones 42

3 Reynolds 36

JOIN

Definition: The SQL JOIN statement is used to combine the data contained in two relational

database tables based upon a common attribute.

Examples: Given the following two tables:

Customers

Customer ID CompanyName Phone

12 ABC Corporation 123-4567

49 XYZ, Inc. 765-4321

Orders

OrderID CustomerID Amount

4021 12 $842.21

8532 12 $582.20

8192 49 $12.43

The following JOIN statement could be used:

JOIN Customers, Orders

WHERE Customers.CustomerID = Orders.CustomerID

DISPLAY Customers.CompanyName, Orders.Amount

Which would display the following results:

CompanyName Amount

ABC Corporation $842.21

ABC Corporation $582.20

XYC, Inc. $12.43

Alternatively, the JOIN can be performed implicitly with a SELECT statement such as:

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SELECT CompanyName, Amount

FROM Customers, Orders

In this example, it is not necessary to specify the JOIN condition because the two tables share

only one common column which is automatically used.  A WHERE clause could be used to

further refine the results.  For example, if we only wanted results from ABC Corporation we

could use the statement:

SELECT CompanyName, Amount

FROM Customers, Orders

WHERE CompanyName = 'ABC Corporation'  

UPDATE

Definition: The UPDATE statement in SQL is used to edit values for attributes in one or more

records of a relational table.

Example: Given the following table:

Members

ID Last Name Age

1 Smith 25

2 Jones 42

3 Reynolds 36

Assume that the member Jones recently changed her last name to McGuire.  This change could

be effected using the following SQL statement:

UPDATE Members

SET LastName = 'McGuire'

WHERE ID = 2

COMMIT

Definition: The COMMIT statement in SQL marks the final step in the processing of a database

transaction.  The alternative is to utilize the ROLLBACK command to cancel the proposed

database changes.

Examples: The COMMIT statement is used in the following manner:

BEGIN TRANSACTION [transaction_name]

...

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SQL Statement(s)

...

COMMIT TRANSACTION [transaction_name]

Rollback

Definition: The ROLLBACK statement in SQL cancels the proposed changes in a pending

database transaction.  The transaction can be rolled back completely by specifying the

transaction name in the ROLLBACK statement.  A partial rollback can also be accomplished by

specifying a savepoint name in lieu of the transaction name.  The alternative to rolling back a

transaction is to utilize the COMMIT command to make the proposed changes part of the

relational database.

Examples: The ROLLBACK statement is used in the following manner to cancel an entire

transaction:

BEGIN TRANSACTION [transaction_name]

...

SQL Statement(s)

...

ROLLBACK TRANSACTION [transaction_name]

The ROLLBACK command can also be used to cancel part of a transaction in the following

manner:

BEGIN TRANSACTION [transaction_name]

...

SQL Statement(s)

SAVE TRANSACTION savepoint_name

SQL Statement(s)

ROLLBACK TRANSACTION savepoint_name

NULL

Definition: The NULL SQL keyword is used to represent either a missing value or a value that

is not applicable in a relational table. 

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