Data Modeling

Lecture Notes 1

Data Modeling

ADBMS Lecture Notes 1: Prepared by Engr. Cherryl D. Cordova, MSIT

1

• Database: A collection of related data. • Data: Known facts that can be recorded and have an implicit meaning.
– An integrated collection of more-or-less permanent data.

• Mini-world: Some part of the real world about which data is stored in a database. For example, student grades and transcripts at a university. • Database Management System (DBMS): A software package/ system to facilitate the creation and maintenance of a computerized database. • Database System: The DBMS software together with the data itself. Sometimes, the applications are also included.
ADBMS Lecture Notes 1: Prepared by Engr. Cherryl D. Cordova, MSIT 2

Evolution of Database System

ADBMS Lecture Notes 1: Prepared by Engr. Cherryl D. Cordova, MSIT

3

Ways of storing data
• Files – ancient times (1960) • Databases
– – – – Hierarchical (1970) Network (1970) Relational (1980) Object (1990)

ADBMS Lecture Notes 1: Prepared by Engr. Cherryl D. Cordova, MSIT

4

File terms
– Record • data items related to a single logical entity (e.g. a student’s information) or row in a table – Field • a place for a data item in a record (first name field in a student record) or a column in a table – File • a sequence of records of the same type (the table)
ADBMS Lecture Notes 1: Prepared by Engr. Cherryl D. Cordova, MSIT 5

File structures
A file: “STUDENT”
ID Last 3 1 record 2 4 Smith Wood Kent Boone field

First Jane Bob

Grade A C B B

Chuck Dan

ADBMS Lecture Notes 1: Prepared by Engr. Cherryl D. Cordova, MSIT

6

File organization
• Serial
– new records appended

• Sequential
– records ordered in file, usually according to a numeric key

ADBMS Lecture Notes 1: Prepared by Engr. Cherryl D. Cordova, MSIT

7

File structures
• Serial
– list of entries in which the order of entry into the list determines the order of the list
ID Last First