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Data Management

Goals
Know the differences between traditional file organization methods and the database approach.
Know how database management systems are used.
Know the importance of a relational database.
Understand how databases are changing business operations across industries.

File Management
Historical Problems
Lacked data mechanisms for:

–  tagging
– retrieving
– manipulating
In other words, everything was custom coded and program specific.

File System Problems
Program/Data Dependence
Data Redundancy 
Lack of Data Integrity
Lack of Data Protection

Databases: A Structured Solution
Databases offer a structured solution. 
A structured collection of data is called a Database.
A collection of tools to implement and manipulate the data is called a Data Base Management System

Database Components
The smallest unit within a database is a field
A related collection of fields is called a record
A related collection of records may be a file
A related collection of files, or a single file, may be a database

Database Functionality
All databases offer analogous functionality including:

– Queries
– Reports
– Forms
– Security
This functionality is implemented in a variety of different ways.

Database Improvements

Reduced data redundancy
Application/data independence
Better control
Flexibility

Database Models
The Hierarchical Model

– Sometimes called Tree Model
– Single Parent, multiple child records
The Network Model
– Multiple parents, multiple child records
The Relational Model
– Structured Tables with well defined relationships

Relational Model Terms
Because Relational Technology is derived from mathematical set theory, its terminology is different than conventional computer terminology. For example:

– Objects -- Entities
– Tuples -- records
– Fields -- attribute
– Relation -- Table
– Joins -- Logical structures that can be dealt with like tables.

Keys
Keys can be used to identify unique records within a table

– Primary Keys
Keys can also used to define the relationship between (join) tables
– Linking (Foreign) Keys
When a key is composed of multiple fields it is called a composite key

The Object-Oriented Structure
Some Object Characteristics

– Encapsulation
– Inheritance
OO is currently being used primarily in Graphics but will become more mainstream in the future.
As operating systems both Windows 95 and Windows NT are said to have object characteristics.

Entity-Relationship Diagrams
Conceptual blueprint for the database
E-R diagrams are graphical representations of all entity relationships.
No standard methodology exists for creating E-R diagrams.

DBMS Components
The Schema
Describes the structure of the database, the names and types of fields in each record type, and the general relationships among different sets of records.
Metadata -- anything that describes the data, but is not data is called metadata (data about data).

DBMS Components
Types of Data

– Numeric
– Alpha
– Graphic
Each type of data can also have a format
– Data types and formats are important because they determine what type of future functionality that your Data Base will have as well as how much storage space that it will need.

DBMS Components
The Data Dictionary

– Contains all the information supplied by the database developer when constructing the schema
 The Data Definition Language (DDL)
– Normally internal to the program and not visible
The Data Manipulation Language (DML)
– Used to query the database

Relational Operations
Popular Relational Data Bases include:

– Oracle
– Access
– SQL Server

Structured Query Language
The DDL and DML of choice.
Originally developed by IBM, it is now an open standard.
SQL commands have an English like structure such as:

– Insert
– Delete
– Select
– Update

Structured Query Language
SQL statements can be embedded in languages such as COBOL and Visual Basic.
SQL routines should be portable across different Data Bases effecting a DB independence.
Graphical front ends are available for some SQL Data Bases.

Popular Database Management Systems
IMS -- A hierarchical DBMS developed by IBM.
FOCUS -- Information Builder
DB2 -- A relational Data Base from IBM 
SQL Server -- A relational Data Base from Microsoft

Database Architecture
Distributed Databases

–  A response to changing environments.
– Countered existing mainframe logic.
Distributed Databases may use Replication.
– Replication is where a copy of the Data Base is replicated at each site that might use it.
 
Replication
Used by many popular programs:
– NT Server
– Lotus Note
– WIN95
Leverages investment in distributed computers.

Client/Server Systems
Shares work between two or more computers.
In two level client server, the front end handles the interface and the back end handles the database.
Multilevel client server generally splits the interface onto the client, the business rules onto a middle layer, and the data base onto the back end.

Data Warehousing and Data Mining
Data Warehousing supports the concept that all of a companies information needs to reside upon a single system.
This system is called the data warehouse.
Once, this is accomplished, the data can be ‘mined’ for relationships that would not be apparent if the data were on different systems.

Jobs
DBA -- Data Base Administrator A person that maintains a data base
Data Base Designer A person that designs and sets up a data base.

Privacy
Large amounts of data in databases can lead to concerns about privacy