the database mis report

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THE DATABASE

Anna Marie G. BalitaMBBA


What is database?

A database is a collection of information that is organized so that it can easily be accessed,

managed, and updated.

Data can be maintained in one of two ways:

Traditional File Approach - no mechanism for tagging, retrieving, or manipulating data

Database Approach - provides powerful mechanism for managing and manipulating data


The Traditional File ApproachDuplicate Data


Drawbacks of Traditional File Approach

Program-Data Dependence• The physical structure and storage of the data files are defined in

the application program code. Making changes to an existing structure are difficult and leads to modification of program which are time-consuming and subject to error.

Data Redundancy (Duplication of data)• Different systems/programs have separate copies of the same data• Multiple file formats, duplication of information in different files

- Waste of space- Data changes in one file could cause inconsistencies- Compromises in data integrity


Drawbacks of Traditional File Approach

Limited Data Sharing• No centralized control of data

- Each application has its own private files & users has little chance to share data outside their own applications

Lengthy Development Times• For each new application programmers must design their own file

formats & descriptions from scratch

Difficulty in accessing data • Need to write a new program to carry out each new task


The Database Approach

• Central repository of shared data• Data is managed by a controlling agent• Stored in a standardized, convenient form

Requires a Database Management System (DBMS)


Database Management System A software system that is used to create, maintain, and provide

controlled access to user databases

Order Filing System

Invoicing System

Payroll System

DBMSCentral database

Contains employee,order, inventory,

pricing, and customer data


Advantages of Database Approach

Program-data independence

Control data redundancy• Attempts to eliminate data duplication by integrating the file

Improved data consistency and integrity• Provides the validity and consistency of stored data

Improved data sharing• Database belongs to the entire organization and can be shared

by all authorized users


Advantages of Database Approach

Improved security• Provides protection of the data from the unauthorized users

Enforcement of standards• The integration of the database enforces the necessary standards

including data formats, documentation standards, update procedures and access rules.

Improved data accessibility and responsiveness• By having an integration in the database approach, data accessing

can be crossed departmental boundaries which provides more functionality and better services to users


Disadvantages of Database Approach

Complexity• DBMS is a complex software. All parties must be familiar with its

functionality.

Size• DBMS consumes a substantial amount of main memory as well as

a large amount of disk space in order to make it run efficiently.

Cost• A multi-user DBMS may be very expensive and usually have high

recurrent annual maintenance cost.


Disadvantages of Database Approach

Cost of conversion• When moving from traditional file-based system to a database

system, the company is required to have additional expenses and training cost.

Performance• As the database approach is to cater for many applications rather

than exclusively for a particular one, some applications may not run as fast as before.



In the database approach, data pieces are organized about entities, - any object about which an organization chooses to collect data, such as people, events, products.

DATA HIERARCHY


The Data Hierarchy

Data Hierarchy refers to the systematic organization of data, often in a hierarchical form. A computer system organizes data in a hierarchy that starts

with bits and bytes and progresses to fields, records, files, and databases.

CHARACTER smallest piece of data, usually a letter or a digit

FIELD single piece of information about entity

RECORD collection of related fields

FILE collection of related records

DATABASE collection of files


The Database ApproachDatabase fields are not limited to holding text and numbers. They can hold pictures, sounds, video clips, and even spreadsheets. Fields can hold any

content that can be digitized.


How data is accessed on the database?

Data is accessed in a database by sending query, a message to the database requesting data from specific records and/or fields and direct the computer to display the results. Modern DBMSs provide fairly user-friendly means of querying a database.



Security and Privacy Issues

Database must be properly secured Not everyone should have access to all data

- Restricting access is managed by customizing menus fordifferent users and requiring users to enter codes that limit access to certain fields or records.

- The database administrator (DBA) sets user limits for access to data in the database.

Users will have different views of the database, based on the data they are allowed to see




Different views from the same

database


Database Models

A database model is the general logical structure in which records are stored within a database and the method used to establish relationships among the records.

Database models differ in:- How records are linked to each other- How users can navigate the database, retrieve records, and create records


Database Models

Common Data Models:

• Hierarchical Model• Network Model• Relational Model• Object-Oriented Model

The relational model is the most widely used model today.


Hierarchical Model

In a hierarchical model, the data is organized into a tree-like structure.

The structure allows repeating information using parent/child relationships: each parent can have many children but each child only has one parent. This structure is simple but nonflexible because the relationship is confined to a one-to-many relationship.

These models were popular in late 1960s, and in 1970. The most widely used hierarchical databases is IMS developed by IBM.


Examples of hierarchical data represented as relational tables

In this model, the employee data table represents the "parent" part of the hierarchy, while the computer table represents the "child" part of the hierarchy. As shown, each employee may possess several pieces of computer equipment, but each individual piece of computer equipment may have only one employee owner.


Network Model

The network model is a variation on the hierarchical model – allowing each record to have multiple parent and child records. Network models generally implement the set relationships by means of pointers that directly address the location of a record on disk. This gives excellent retrieval performance, at the expense of operations such as database loading and reorganization.

Some well known DBMS using Network Model:• Honeywell IDS (Integrated Data Store)• IDMS (Integrated Database Management

System)


Relational ModelThe relational model represents the database as a collection of relations.

Each relation resembles a table of values.

When a relation is thought of as a table of values, each row in the table represents a collection of related data values.

• To design a relational database, you must understand the entities to be stored in the database and how they relate

• Tables are independent of each other, but can be related to each other


Relational Model

A row is called a tuple A column header is called an attribute The table is called relation


Relational Keys

To retrieve records from a relational database, or to sort them, you must use a key. A key is a field whose values identify records either for display or for processing. You can use any field as a key.

Keys are crucial to a table structure for the following reasons:

They ensure that each record in a table is precisely identified. They help establish and enforce various types of integrity. They serve to establish table relationships.


Relational Keys

Super Key A Super key is any combination of fields within a table that uniquely identifies each record within that table.

Candidate Key A candidate is a subset of a super key. A candidate key is a single field or the least combination of fields that uniquely identifies each record in the table. The least combination of fields distinguishes a candidate key from a super key. Every table must have at least one candidate key but at the same time can have several.


Relational Keys

As an example, we might have a student_id that uniquely identifies the students in a student table. This would be a candidate key. But in the same table we might have the student’s first name and last name that also, when combined, uniquely identify the student in a student table. These would both be candidate keys.


Relational Keys

Primary Key A primary key is a candidate key that is most appropriate to be the main reference key for the table. As its name suggests, it is the primary key of reference for the table and is used throughout the database to help establish relationships with other tables.

The primary key must contain unique values, must never be null and uniquely identify each record in the table. In the given table, the candidate key student_id is the most appropriate primary key


Relational KeysForeign Key A foreign key is generally a primary key from one table that appears as a field in another where the first table has a relationship to the second

An example might be a student table that contains the course_id the student is attending. Another table lists the courses on offer with course_id being the primary key. The 2 tables are linked through course_id and as such course_id would be a foreign key in the student table


Relational Model

Join TableA combination of data from two or more tables. A table might include foreign keys from several tables, offering flexibility in creating reports with related data from several tables.

Two types of table relationships:• One-to-many relationship: one item in a table is linked to many

items in the other table• Many-to-many relationship: many items in a table are linked to

many items of the other table


Object-Oriented ModelThe object-oriented database model uses the object-oriented

approach to maintaining records. In object-oriented technology, an object consists of both data and the procedures that manipulate the data.

EncapsulationThe combined storage of both data and the procedures that manipulateit. Through encapsulation, an object can be “planted” in different data sets.

InheritanceThe ability in object-oriented structures to create a new object automatically by replicating all or some of the characteristics of a previously developed object (called the parent object).


Object-Oriented Model The relationships between data about entities are not managed by way of

foreign keys, but through the relationships of one object with another.

One advantage of this approach is the reduction of data redundancy.

Object-oriented databases (ODBs) do not store records, but data objects(such as drawings, maps and Web pages), which is an advantage for quick updates of data sets and the relationships among them.

All these capabilities make object-oriented DBMSs handy in computer-aided design (CAD), geographic information systems, and applications used to update thousands of Web pages daily, because they can handle a wide range of data—such as graphics, voice, and text—more easily than the relational model.

the database mis report

Documents

data database approach

data duplication

data formats

data files

data integrity

data need

file improved data consistency

improved data accessibility