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Database Assignment Help
http://www.myassignmenthelpers.com/
Type of Data to Store
Type of Data◦Raw data◦Pre-processed◦Compressed
Frequency of Data Storage for Sensor Data◦Tradeoff between precision and quantity
Database Types / Data Models
RelationalOOHybrid (Object-Relational)TemporalDeductiveOthers
◦Spatial, …
Data Representations
Relational◦We all know…flat tables of atomic attributes
with foreign key relationshipsOO
◦Complex data reps multivalued, composite
Temporal◦Relational model: add valid start, end dates to
each table (versions of info and when valid)◦Includes time, events, durations…
Operations
DDL/DML (data def/manip languages)◦SQL◦OQL
Update operations◦Built-in insert, delete, update◦Stored procedures for triggers, active (ECA)
rules
Example Operations for Temporal Databases
INCLUDES◦Rows valid in a certain time period
BEFORE/AFTER a time conditionSet operations
◦Union, intersection of 2 time periods
Distributed vs. Centralized
Centralized database can produce a bottleneck ◦Large volume of data input◦Large database◦Large volume of queries
In distributed databases, data consistency, replication, and retrieval can be more problematic◦Consistency of schemas◦Retrieval in case the data location is not known◦Communication overhead to ensure database
consistency
Types of Database Systems
Commercial◦DB2◦Empress◦ Informix◦Oracle◦MS Access◦MS SQL◦Sybase
Free◦Berkeley DB◦PostgreSQL◦MySQL
Database System
Database:A collection of related data.
Data:Known facts that can be recorded and have an implicit meaning.
Database Management System (DBMS):A software package/system to facilitate theDefine, Construct, Manipulate and Share
functions of a computerized database.
Typical DBMS Functionality
Define a particular database in terms of its data types, structures, and constraints
Construct or Load the initial database contents on a secondary storage medium
Manipulate the database:◦ Retrieval: Querying, generating reports◦ Modification: Insertions, deletions and updates to its content◦ Accessing the database through Web applications
Share a database allows multiple users and programs to access the database simultaneously
Database system environment
Example
A UNIVERSITY database for maintaining information concerning students, courses, and grades in a university environment
We have:STUDENT file stores data on each studentCOURSE file stores data on each courseSECTION file stores data on each section of each courseGRADE_REPORT file stores the grades that students
receive PREREQUISITE file stores the prerequisites
Example of a simple database
Database manipulation
Database manipulation involves querying and updating
Examples of querying are:Retrieve a transcriptList the prerequisites of the “Database”
courseExamples of updating are:Enter a grade of “A” for “Smith” in
“Database” course
Advantages of using the DBMS approach
Restricting unauthorized access to dataProviding Storage Structures (e.g.
indexes) for efficient Query ProcessingProviding backup and recovery servicesProviding multiple interfaces to different
classes of usersRepresenting complex relationships
among data