ETEC 100 Information Technology Lecture Introduction to database

Learning Objectives Define and understand the following terms: data, information, database, database management system (DBMS), database system, metadata Compare and contrast conventional file systems and database systems. Identify advantages of database approach over traditional file systems

What is database? Database: An organized collection of logically related data Data: Known facts that could be recorded and stored on computer media Facts could be in any format: text, graphics, images… Information: Processed data that could be used to increase the knowledge of the user Closely related to data, but different View data as “raw material” and information as “intermediate product” The final product is “knowledge”

Data, Information and Knowledge A. Berger M. Jones T. Martin J. Smith Shoes Scarves Jewelry Groceries A. Berger is most likely to buy new product John Smith Taurus Database Queries ? wireless 50,000 234 Ted Martin Amex Gold Anna Berger 50,000 46,800 29,200 75,500 MoU Qty Income Education B.A. T. Martin is profitable customer and is likely to switch carriers shoes Data Information Knowledge & Customer Insight Some of the images above come from a presentation given by: ®

Databases Interact with DBs many times in a day Database processing integral part of many businesses Keep track of things (what sort of things?)

History of data collection methods Manual System File System Database System

Manual Filling Systems Before computer: Manual Filing Systems Still used in many everyday activities Usually organize data in a logical way Ex;bills…….. Problems with Manual Filling Systems Small –scale Hard to analyze: ‘ How many students enrolled in MIS ?

Traditional File-Based processing Application programs were written specifically for the data file structure that was to be used, so: A change in the data file structure required change in an application program(s) that needed that data

File Processing Systems: An example Data Entry End Users File Management Programs File Report Programs Data Files Separated systems, separated files, separated data Both file management programs and file report programs have describe WHAT data to write / read and HOW to do that

File Processing Systems: Problems Isolation of Data/ Limited Data Sharing Isolation between departments file systems Isolation in a department file system: Duplication of Data Duplicated data waste storage space Duplicated data result in loss of data integrity Lack of Data Independence If we change the data type of address from 40 characters to 41 characters, all related programs have to change accordingly

Database Systems: Basic Terms Database: An organized collection of logically related data Database Management Systems (DBMS): A software package to facilitate the creation and maintenance of a database. Database system: a computerized record-keeping system, containing database and DBMS as well as some other components. Four components: Users, Software, Hardware, Data

Database Systems: Basic Terms End users Software interact Application Programmers Application Programs develop “What” to get Database Administrators DBMS maintain “How” to get Data Database Designers design Database Users

Database Systems: Advantages Data are stored in a central repository, managed by DBMS Data sharing is easy Reduce duplication to minimum: one table for each entity Inconsistency can be avoided to some extent by enforcement of integrity constraints Metadata offers data abstraction Data independence: If format needs to be changed, simply update the metadata. Application programs are not affected Structural independence: similar to the above

Data Elements in a Database User data (files) relations in a table format (e.g. Relational Database) Metadata (systems tables) data about data, data dictionary meaning of terms, description of structure etc. Indexes (overhead data) improves performance and accessibility Application Metadata structure & format of forms, reports, & queries etc.

Database Development Process Requirement Analysis Conceptual Design Logical Design Physical Design Implementation Maintenance

Database Development Process Requirements Analysis Collect and Analyze the requirements of the users. Conceptual Design Design a conceptual model, e.g., ER model. Logical Design Translate the conceptual model into the logical model Normalization. Physical Design Define the database and write application programs. Implementation Write, test, and install programs that process the database MaintenanceUse maintain, and “tune” the database

Relational Database A relational database is one in which the data consists of a collection of tables related to each other through common values. The two most prominent characteristics of a relational database are data stored in tables relationships between tables

Table

Relation Two-dimensional table Rows are tuples Columns are attributes Equivalent Terms:

Characteristics of a relation a relation has a unique name within same DB each cell contains one single value each attribute within a given relation has a distinct name values of an attribute are from the same domain order of attributes has no significance order of rows has no significance no duplicate rows

Key “a group of one or more attributes (columns) that uniquely identifies a tuple (row)”

Relational Database Keys Candidate key Primary key: candidate key selected to uniquely identify all table rows Foreign key: attributes(s) in one table whose values must match primary key in another table

Relationships

Referential Integrity Rule If a foreign key exists in a relation, either the foreign key value must match a candidate key value of some tuple in its home relation or the foreign key value must be wholly null Therefore:- if B references A then A must exist

Schema A schema is an abstract representation of database entities and objects. A schema helps us design a database diagrammatically before we start creating it.

Schema (cont.)

Query Requests for information from a database are made in the form of a query. The set of rules for constructing queries is known as a query language. query language called SQL (structured query language) For example, the query -requests all recordsfrom customer table in which the NAME field is SMITH and the AGE field is greater than 35.

SQL (structured query language) For example, the query -requests all recordsfrom customer table in which the Name field is SMITH and the Age field is greater than 35. SELECT ALL FROM Customer WHERE Name = "SMITH" and age > 35