1. CS4222 Principles of Database System
3/24/2018
CS4222 Principles of Database System
1. Introduction
Huiping Guo
Department of Computer Science
California State University, Los Angeles

2. Some concepts Database Data Database Management System (DBMS)
Fall 2005
Some concepts
Database
A very large, integrated collection of data.
Data
Known facts that can be recorded and have an implicit meaning
Database Management System (DBMS)
a software package that enables users to create and maintain databases
Facilitates the processes of defining, constructing, manipulating, and sharing databases among various users and applications
Database System:
The DBMS software together with the data itself. Sometimes, the applications are also included.
1. Introduction CS4222_Summer'17

3. Simplified database system environment
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4. 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
Manipulating the database:
Retrieval: Querying, generating reports
Modification: Insertions, deletions and updates to its content
Accessing the database through Web applications
Processing and Sharing by a set of concurrent users and application programs – yet, keeping all data valid and consistent
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5. Typical DBMS Functionality
Other features:
Protection or Security measures to prevent unauthorized access
“Active” processing to take internal actions on data
Presentation and Visualization of data
Maintaining the database and associated programs over the lifetime of the database application
Called database, software, and system maintenance
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6. Example of a Database Miniworld Mini-world for the example:
A database represents some aspect of the real world
Mini-world for the example:
Part of a UNIVERSITY environment.
Some mini-world entities:
STUDENTs
COURSEs
SECTIONs (of COURSEs)
(academic) DEPARTMENTs
INSTRUCTORs
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7. Example of a Database (with a Conceptual Data Model)
Some mini-world relationships:
SECTIONs are of specific COURSEs
STUDENTs take SECTIONs
COURSEs have prerequisite COURSEs
INSTRUCTORs teach SECTIONs
COURSEs are offered by DEPARTMENTs
STUDENTs major in DEPARTMENTs
Note: The above entities and relationships are typically expressed in a conceptual data model, such as the ENTITY-RELATIONSHIP data model (to be discussed in details later)
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8. Example of a simple database
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9. Main Characteristics of the Database Approach
Self-describing nature of a database system:
A DBMS catalog stores the description of a particular database (e.g. data structures, types, and constraints)
The description is called meta-data.
This allows the DBMS software to work with different database applications.
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10. Example of a simplified database catalog
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11. Main Characteristics of the Database Approach (continued)
Insulation between programs and data:
Called program-data independence.
Allows changing data structures and storage organization without having to change the DBMS access programs
The characteristic that allows program-data independence is called data abstraction
Support of multiple views of the data:
Each user may see a different view of the database, which describes only the data of interest to that user.
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12. Main Characteristics of the Database Approach (continued)
Sharing of data and multi-user transaction processing:
Allowing a set of concurrent users to retrieve from and to update the database.
Concurrency control within the DBMS guarantees that each transaction is correctly executed or aborted
Recovery subsystem ensures each completed transaction has its effect permanently recorded in the database
OLTP (Online Transaction Processing) is a major part of database applications. This allows hundreds of concurrent transactions to execute per second.
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13. Database Users Users may be divided into
Those who actually use and control the database content, and those who design, develop and maintain database applications (called “Actors on the Scene”)
Those who design and develop the DBMS software and related tools, and the computer systems operators (called “Workers Behind the Scene”).
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14. Database Users Actors on the scene Database administrators:
Responsible for authorizing access to the database, for coordinating and monitoring its use, acquiring software and hardware resources, controlling its use and monitoring efficiency of operations.
Database Designers:
Responsible to define the content, the structure, the constraints, and functions or transactions against the database. They must communicate with the end-users and understand their needs.
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15. Advantages of Using the Database Approach
Controlling redundancy in data storage and in development and maintenance efforts.
Restricting unauthorized access to data.
Providing Storage Structures (e.g. indexes) for efficient Query Processing
Providing persistent storage for program Objects
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16. Advantages of Using the Database Approach (continued)
Providing backup and recovery services.
Providing multiple interfaces to different classes of users.
Representing complex relationships among data.
Enforcing integrity constraints on the database.
Permitting inferences and actions using deductive and active rules
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17. File systems vs a DBMS Scenario
A university wishes to store large collection of data on faculty, departments, students, and so on
The data will be accessed by different faculty, departments, students for various reasons
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18. Storing the data in files (cont.)
Goal
Find the names of all faculty in a department
Solution
Write a procedure to search files for matching faculty
Problems
-query is hard-coded, requires program
-new queries require re-programming
-no theory for query optimization
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19. Storing the data in files (cont.)
Goal: Data should be free of inconsistencies
A student cannot get both B and A in the same course
Solution
make sure procedures verify data is valid
Problems:
integrity constraints cannot be found or changed without re-programming
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20. Storing the data in files (cont.)
Goal
Data should be secure from unauthorized users
Solution
use file access permissions
Problems:
host OS may not provide any file access restrictions
file access permission provided by host operating system will be inadequate
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21. Database solution Create an application to which we input:
what our data will look like
what constraints apply to the data
allows us to pose arbitrary queries
allows us to specify access controls
monitors modification of data
The database is generic
works with anyone’s data or queries -at run time
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22. Describing and Storing Data in a DBMS
Fall 2005
Describing and Storing Data in a DBMS
data model
Data can be represented in different ways
Trees, graphs, tables, etc.
A data model is a way to represent data
relational data model
using tables to represent data
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23. Relational data model Relation Schema A table with rows and columns.
Conceptual schema (logical schema)
Describes the columns, or fields of relations
Physical schema
File organizations
Indices
External schema
A collection of views from the conceptual schema
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24. Levels of Abstraction View 1 View 2 View 3 Conceptual Schema
Fall 2005
Levels of Abstraction
View 1
View 2
View 3
Conceptual Schema
Physical Schema
disk
Schemas are defined using DDL; data is modified/queried using DML.
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25. Example: University Database
Fall 2005
Example: University Database
Conceptual schema:
Courses(cid: string, cname:string, credits:integer)
Faculty(fid:string, fname:string, sal:real)
Teaches(cid:String, fid:string)
Physical schema:
Relations stored as unordered files.
Index on first column of Students.
External Schema (View):
Course_info(cid:string,fname:string)
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26. Fall 2005
Data Independence *
Applications insulated from how data is structured and stored.
Logical data independence
Protection from changes in logical structure of data.
Physical data independence
Protection from changes in physical structure of data.
One of the most important benefits of using a DBMS!
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27. Logical data independence example
Suppose logical schema has been changed
Faculty_public(fid:string, fname:string, office:string)
Faculty(fid:string, sal:real)
Need to change the definition of the view course_infor
The applications that use Course_infor remain the same
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28. Queries in a RDBMS Relational calculus Relational algebra
A formal query language based on mathematical logic
Relational algebra
Anther formal language based on a collection of operators for manipulating relations
Structured Query Language (SQL)
Data Manipulation language (DML)
Data Definition Language (DDL)
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29. What will be covered Database design Database Implementation
Data modeling
Entity-Relationship (ER) model
ER diagram  relational model
Normalization
Database Implementation
Data Definition Language (DDL)
Authorization
Integrity constraints
Stored procedures and triggers
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30. What will be covered Query Languages Application Development
Relational calculus and algebra
DML
queries, subqueries, nested queries, joins
Application Development
Embedded SQL
JDBC
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