[ Databases ] - Data Modeling and Database Design

What is a Database?

: a collection (Not a random pile of data) of data that exists over a long period time.

 

 

DBMS

: a complex software package developed to store and manage databases

è Mysql, mongoDB, …

è Provide convenient, efficient, and secure access and manipulation of large amounts of data

è Controls access to shared data from multiple, simultaneous users with properties Atomicity, Consistency, lsolation, Durability (ACID)

 

 

Data base system(DBS) = Database + DBMS

 

 

Disadvantages of FPS

: redundancy of data – identical data are distributed over various files (major problem)

 

VS

 

Advantages of Databases

-       Minimize data redundancy and avoid inconsistency.

-       Centralized control over data management

-       Data abstraction, independence

-       Concurrent access to shared data

-       Security, authorization

 

 

 

Types of Data Models

-       ER (Entity- Relationship) model

-       Relational Model

-       ODL (Object-Oriented Data Model)

-       Logical Data Model (Datalog)

 

 

Relational Model

: data is organized in relations (tables)

** relations = tables

 

 The user shouldn’t be concerned with the underlying storage data structure.

 Most widely used model

 Another approach: object – relational model

 

Relational databases schema

è Set of table names : D  = {R1, …., Rn}

è Set of attributes for each table : R = {A1,…, Ak}

 

 

Goals of Database System

: DB system should be simple but also complex (so that many queries and transactions could be handled efficiently

 

 

Three Views | Level of Data

1)    External (logical) level : user view

2)    Conceptual (logical) level : an outcome of a database design

3)    Internal (physical) level : describes the storage structure of data and the indexes