File Systems and DatabasesProf. Sin-Min Lee
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Text Book
NARAYAN S. UMANATH & RICHARD W. SCAMELL, DATA MODELING AND DATABASE DESIGN, 2007 Thomson
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A. Silberschatz, H.F. Korth, S. Sudarshan: Database System Concepts, 5th Ed., McGraw-Hill, 2006.
GOOD REFERENCE
Files and Databases
File: A collection of records or documents dealing with one organization, person, area or subject (Rowley)
Manual (paper) files
Computer files
Database: A collection of similar records with relationships between the records (Rowley)
Bibliographic, statistical, business data, images, etc.
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Sales per Employee for Each of ROBCOR’S Two Divisions
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Database
A Database is a collection of stored operational data used by the application systems of some particular enterprise (C.J. Date)
Paper “Databases”
Still contain a large portion of the world’s knowledge
File-Based Data Processing Systems
Database Management Systems (DBMS)
History
50’s and 60’s all applications were custom built for particular needs
File based
Early DBMS were extensions of programming languages
1970 - E.F. Codd and the Relational Model
1979 - Ashton-Tate and first Microcomputer DBMS
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Inconsistent data
Data accessibility and responsiveness
Data independence
Physical representation and location of data and the use of that data are separated
The application doesn’t need to know how or where the database has stored the data, but just how to ask for it
Moving a database from one DBMS to another should not have a material effect on application program
Recoding, adding fields, etc. in the database should not affect applications
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Its query language allows quick answers to ad hoc queries.
It provides end users better access to more and better-managed data.
It promotes an integrated view of organization’s operations -- “big picture.”
It reduces the probability of inconsistent data.
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Between the End User and the Database
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A well-designed database facilitates data management and becomes a valuable information generator.
A poorly designed database is a breeding ground for uncontrolled data redundancies.
A poorly designed database generates errors that lead to bad decisions.
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Its simple characteristics facilitate understanding of the design complexity of a database.
It provides useful knowledge for converting a file system to a database system.
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Data
“Raw” facts that have little meaning unless they have been organized in some logical manner. The smallest piece of data that can be “recognized” by the computer is a single character, such as the letter A, the number 5, or some symbol such as; ‘ ? > * +. A single character requires one byte of computer storage.
Field
A character or group of characters (alphabetic or numeric) that has a specific meaning. A field might define a telephone numbers, a birth date, a customer name, a year-to-date (YTD) sales value, and so on.
Record
A logically connected set of one or more fields that describes a person, place, or thing. For example, the fields that comprise a record for a customer named J. D. Rudd might consist of J. D. Rudd’s name, address, phone number, date of birth, credit limit, unpaid balance, and so on.
File
A collection of related records. For example, a file might contain data about ROBCOR Company’s vendors; or, a file might contain the records for the students currently enrolled at Gigantic University.
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“Raw” facts that have little meaning unless they have been
organized in some logical manner. The smallest piece of data
that can be “recognized” by the computer is a single
character, such as the letter A, the number 5, or some
symbol such as;
byte of computer storage.
A character or group of characters (alphabetic or numeric)
that has a specific meaning. A field might define a telephone
numbers, a birth date, a customer name, a year-to-date
(YTD) sales value, and so on.
Record
A logically connected set of one or more fields that describes
a person, place, or thing. For example, the fields that
comprise a record for a customer named J. D.
Rudd might
of birth, credit limit, unpaid balance, and so on.
File
A collection of related records. For example, a file might
contain data about ROBCOR Company’s vendors; or, a file
might contain the records for the students currently enrolled
at Gigantic University.