Akram Jalal Ahlia University MIS College of Business and Finance 1.

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ITMA 322: Database Management

Systems

Akram JalalAhlia University

MISCollege of Business and Finance

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COURSE IDENTIFICATION

LECTURES: M 16:30 – 18:10 - Class 6.

Lab: W 16:30 – 18:10 - Lab 1.

INSTRUCTOR: Dr. Akram Jalal Office:

Email: [email protected]

Phone:

Office Hours: Tuesdays, 10am to 11:30am Walk-ins are welcome any time based on availability

Dr. Akram Jalal

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ASSIGNMENTS: Submissions will be in class. Late submissions will be

penalized by at the rate of 10% per day. Assignments later than three days will not be accepted.

Assignment should be written using computer tool. Hand writing home works are not accepted.

All students should achieve their own work according to the Ahlia University rules, which means you must write up your favourite solution independently.

Exams: The midterm exam will be given in-class on ----. This

exam will covers material and chapters (1, 2 and 5). The date of final exam is based on the final exam

timetable.

COURSE IDENTIFICATION (cont)

http://www.stanford.edu/dept/vpsa/judicialaffairs/guiding/honorcode.htm

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GRADING:

Attendance: 10%

Assignment: 20%,

Midterm: 30%,

Final: 40%.

Consistent class attendance is required absences will seriously affect your total grade.

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by Raghu Ramakrishnan & Johannes Gehrke◦ 3rd edition

Available: Next week in the library

The readings of this book are required, even if material is not covered in the lectures. All other readings are optional.

Textbook: Database Management Systems

Course Structure (Outline)

WeekHours

ILOs Topics Teaching Method Assessment MethodLecture Lab1 3 --- A1 Course Introduction & Familiarisation Lectures-

Class discussionsOral Participation

2 3 --- A1, A2,B1, B2,B3, C3,D2, D4

Introductions to DBMSLectures-

Class discussions

Oral Participation/Group

discussions

3 1,1/2 1,1/2 A1, B2, B3, C1, C3

Database design Lectures-Class discussions-

Lab Exercises


discussions4 1,1/2 1,1/2 A1, B2, B3, C1,

C3Database design Lectures-

Class discussions- Lab Exercises


discussions5 1,1/2 - A1, A3, B3, D3 Structured Query Language (SQL)

1. Basic SQL queryLectures-



Assignment

5 1,1/2- B1, C1, C3, D4,

D3All topics weeks 2-5. -- Midterm Exam

6 1,1/2 1,1/2 A1, A3, B3, D3 Structured Query Language (SQL)1. Basic SQL query

Lectures-Class discussions-

Lab Exercises


Assignment7 1,1/2 1,1/2 A1, A3, B3, D3 Structured Query Language (SQL)

1. Union Intersection and ExceptionLectures-




1. Union Intersection and ExceptionLectures-




1. Aggregate operatorsLectures-



Assignment10 3 - A1, A3, B2, B3,

C1, C3Tree Structured Indexing Lectures-

Class discussionsOral Participation

/GroupDiscussions

11 3 - A1, A3, B2, B3, C1, C3

Tree Structured IndexingSubmitting assignment 1

Lectures-Class discussions


discussions12 3 - A2, A3,

B1, B3,D2, D4

Transaction Management Lectures-Class discussions


discussions13, 14 6 A2, A3,

B1, B3,D2, D4

Concurrency Control & crash recovery Lectures-Class discussions


discussions15 2 A1, A2,

A3, B1,B3, C1,C3, D3

RevisionLectures-

Class discussions


discussions

16-17 2 - All Topics but especially weeks 8-15 -- Final Examination

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A large, integrated collection of data, typically describing the activities of one or more organizations.

Models a real-world enterprise, e.g. a university database might contain information about:◦ Entities such as:

students, courses, instructors, ◦ Relationships

One to One One to Many Many to Many

A Database Management System (DBMS) is a software designed to assist in maintaining and utilizing large collection of data.

DBMS also needed to store the data in files and write application-specific code to manage it.

What Is a Database?

Data independence.DBMS provides an abstract view of the data that hides data representation

and storage.When the DBMS hides certain details of how data is stored and

maintained, it provides what is called as the abstract view of data. Complexity (of data and data structure) is hidden from users through several levels of abstraction.

Efficient data access.DBMS utilizes a variety of sophisticated techniques to store and retrieve

data efficiently. Data integrity and security.

If data is always accessed through DBMS, the DBMS can enforce integrity constrains.

E.g.1. Before inserting salary, DBMS should check that department budget is not exceeded. E.g.2 access control.

Uniform data administration. When several users share the data, centralizing the administration of

data can offer the significant improvement. Concurrent access, recovery from crashes.

DBMS schedules concurrent access to the data in such a manner that users can think of the data as being accessed by only one user at a time.

Reduced application development time: DBMS supports important functions that are common to many applications

accessing data in DBMS

Why Use a DBMS?

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1. Large data sets (100s of GBs, or TBs, …)

No indices◦ Finding “George” in huge flat file is expensive

Modifications intractable without better data structures◦ “George” “Georgie” is very expensive◦ Deletions are very expensive

Problems without a DBMS...

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4. Security?◦ File system may lack security features◦ File system security may be rough

5. Application programming interface (API)? Interfaces, interoperability

6. How to query the data?

Problems without an DBMS...

A data model is a collection of high level data description constructs. Most of DBMS today are based on relational data model.

Semantic data model (such as E-R diagram) is more abstract, high level data model and served as starting point and subsequently translated into a database design.E-R diagram allows us to periodically denote entities and the relationships among them.

A schema is a description of a particular collection of data, using the a given data model.

e.g. Student (Sid: string, Name: String, age: Integer)

The relational data model is the most widely used model today (which is used in numerous systems such as Oracle, DB2, MS Access) is based on relation (which described as a set of records) , basically a table with rows and columns.◦ Every relation has a schema, which describes the fields (columns, or

attributes).◦ Other data models are: Hierarchical model, the network model, object-oriented

model and object-relational model.

Data Models

Levels of Abstraction Data in DBMS is described at

three levels of abstractions. Many External echemas, single

conceptual (logical) schema and physical schema.◦ Views describe how users see the

data. ◦ Conceptual schema defines logical

structure. In RDBMS CS describes all relations that are stored in the database.

Student(sid: string, Name: String, age: Integer)Faculty ( …..

◦ Physical schema describes the files and indexes used. It summarizes how the relations described in the conceptual schema are actually stored on secondary storage devices such as disks and tapes.

External schema allow data access to be customized (and authorized). DDL (data definition Language) used to define external and conceptual schemas). Concerned with the way individual users see the data. Information about those schemas are stored in system catalogs.

Physical Schema (one per

each DB)

Conceptual Schema (one per

each DB)

External schema –View1

External schema – view 2

External schema - view3

Each external schema consists of one or more

relations and view

User 1

User 2

User 3

User 4

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Start with SQL DDL to create tables:

Continue with SQL to populate tables:

How the programmer sees the DBMS

CREATE TABLE Students (Name CHAR(30)SSN CHAR(9) PRIMARY KEY NOT NULL,Category CHAR(20)

);

CREATE TABLE Students (Name CHAR(30)SSN CHAR(9) PRIMARY KEY NOT NULL,Category CHAR(20)

);

INSERT INTO StudentsVALUES('Hillary', '123456789', 'undergraduate');INSERT INTO StudentsVALUES('Hillary', '123456789', 'undergraduate');

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Ultimately files, but complex

How the programmer sees the DBMS

SSN Name Category 123-45-6789 Hillary undergrad 234-56-7890 Barak grad … …

Students:

CID CName C20.0046 Databases C20.0056 Advanced Software

Courses:

SSN CID semester 123-45-6789 C20.0046 Spring,

2004 123-45-6789 C20.0056 Spring,

2004 234-56-7890 C20.0046 Fall, 2003 …

Takes:

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Find all the students who have taken C20.0046:

Find all the students who have taken C20.0046 previously:

Find the students’ names:

Querying: Structured Query Language

SELECT SSN FROM TakesWHERE CID='C20.0046';SELECT SSN FROM TakesWHERE CID='C20.0046';

SELECT SSN FROM TakesWHERE CID='C20.0046' AND Semester='Fall, 2005';

SELECT SSN FROM TakesWHERE CID='C20.0046' AND Semester='Fall, 2005';

SELECT Name FROM Students, TakesWHERE Students.SSN=Takes.SSN AND CID='C20.0046' AND Semester='Fall, 2005';

SELECT Name FROM Students, TakesWHERE Students.SSN=Takes.SSN AND CID='C20.0046' AND Semester='Fall, 2005';

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Conceptual Schema:◦ Students(ssn: string, name: string, login: string, age:

int, gpa: real)◦ Courses(cid: string, cname: string, credits: int)◦ Enrolled(sid:string, cid:string, grade: string)

Physical schema:◦ Relations stored as unordered text files.◦ Indices on first column of each relation

Views:◦ My_courses(cname: string, grade: string, credits: int)◦ Course_info(ssn: string, name: string, status: string)

Schema e.g.: University registrar

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failover/rovery concurrent use deal with large datasets? security interop? querying in what?

DBMS as application Q: How does a DBMS solve these problems? A: See third part of course, but for now…

system must support

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Consider a database that holds information about airline reservations. At any time, it is possible that several travel agents are looking up information about available seats on various flights and making new seat reservations.

When several users access a database concurrently, the DBMS must order their requests to avoid conflicts.

ACID test properties ◦ Atomicity

all or nothing◦ Consistency

constraints on relationships◦ Isolation

concurrency control simulated solipsism

◦ Durability Crash recovery

Transaction processing

Key concept is transaction, which is an atomic sequence of database actions (reads/writes).

Each transaction, executed completely, must leave the DB in a consistent state if DB is consistent when the transaction begins.

Transaction: An Execution of a DB Program

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Avoiding inconsistent state A DBMS prevents this outcome

◦ Xacts are all or nothing

One simple idea: log progress of and plans for each xact◦ Durability: changes stay made (with log…)◦ Atomicity: entire xact is committed at once

Atomicity & Durability

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Many users concurrent execution◦ Disk access is slow (compared to CPU)◦ don’t waste CPU – keep running

Interweaving actions of different user programs but can lead to inconsistency:

◦ e.g., two programs simultaneously withdraw from the same account

For each user, should look like a single-user system

Isolation

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Each xact (on a consistent DB) must leave it in a consistent state

Consistency

Concurrent execution of user programs is essential for good DBMS performance.◦ Because disk accesses are frequent, and relatively

slow, it is important to keep the cpu humming by working on several user programs concurrently.

Interleaving actions of different user programs can lead to inconsistency: e.g., check is cleared while account balance is being computed.

DBMS ensures such problems don’t arise: users can pretend they are using a single-user system.

Concurrency Control

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Database design:◦ Entity/Relationship models◦ Modeling constraints

The relational model: ◦ Relational algebra◦ Transforming E/R models to relational schemas

SQL◦ DDL & query language

Course outline

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Why would you choose a database system instead of simply storing data in operating system files? When would it make sense not to use a database system?

Explain the difference between external, internal, and conceptual schemas. How are these different schema layers related to the concepts of logical and physical data independence?

Which of the following plays an important role in representing information about the real world in a database? Explain each of briefly.

1. The data definition language (DDL).2. The data manipulation language (DML).3. The buffer manager.4. The data model (DM).

End chapter exercises

Akram Jalal Ahlia University MIS College of Business and Finance 1.

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