ITM 102 Lecture Notes - Lecture 6: Relational Database Management System, Database, Unique Key

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ITM102 Lecture 6- Databases and Information Management
Organizing Data in a Traditional File Environment
Bit: Smallest unit of data; binary digit (0,1)
Byte: Group of bits that represents a single character
Field: Group of words or a complete number
Record: Group of related fields
File: Group of records of same type
Database: Group of related files
Entity: Person, place, thing, event about which information is maintained
Attribute: Description of a particular entity
Key field: Identifier field used to retrieve, update, and sort a record
Problems with the Traditional File Environment
Data redundancy and inconsistency
Data redundancy: is the presence of duplicate data in multiple data files so that the same data
are stored in more than one place or location
Program-data dependence
Refers to the coupling of data stored in files and the specific programs required to update and
maintain those files
Lack of Flexibility
A traditional file system can deliver routine schedule reports after extensive programing efforts,
but it cannot deliver ad-hoc reports or respond to unanticipated information requirement timely
Poor security
Management may have no way of knowing who is accessing or even making changes to the
organization’s data
Lack of data sharing and availability
Information cannot flow freely across different functional areas or different parts of the
The database approach to data management
DBMS: is a software that permits an organization to centralized data, manage them efficiently,
and provide access to the stored data by application programs
How a DBMS solves the problems of the traditional file environment
Relational DBMS
Represent data as two-dimensional tables called relations
Relates data across tables based on common data elements
Access, oracle
Key field: The field for supplier_number in the supplier table uniquely identifies each record so
that the record can be retrieved , updated or sorted
Primary key: each table in a relational database has one field that is designated
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