Lecture 1: Introduction to Database - Nubacad.com

Hierarchical Model
• Stores data as hierarchically related to each other.
Record shape are tree structure.
• Logically represented by an upside down tree
• Each parent can have many children
• Each child has only one parent
NUB
Network Model
A network database is similar to hierarchical DBMS, but
each child record can have more than one parent record.
Thus a child record may be reached through more than one
parent.
University class scheduling system
CIT 1101 CIT 3303 MIS 4102
Faculty of
Science
Faculty of
Business
SMR BA ZH
CSE
CS
BBA
MBA
Student 1 Student 2 Student 3 Student 4 Student 5
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DBMS Languages
• Data-Definition Language (DDL) : DDL concerned
with defining the structure of the database.
• Data-Manipulation Language (DML): DML
concerned with querying and manipulating the data
in the database. They are basically two types:
• Procedural DMLs: Procedural DMLs require a
user to specify what data are needed and how to
get those data.
• Nonprocedural DMLs: Nonprocedural DMLs
require a user to specify what data are needed
without specifying how to get those data.
Goals of Database Design
It is important to design the database in such a way
that:
• A specific item can be reached easily
(maximum guarantee that the desired record will be reached)
• The database can respond to the user’s different questions
easily (necessary relationships are provided)
• The database occupies minimum storage space (choosing
data types and how to express a certain concept is important)
• The database contains no unnecessary data
(storing the gross salary is enough, the net salary can be
calculated from the gross salary)
• Data can be added and updated easily
without causing mistakes (no data redundancy)
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