L1: Course Overview & Review

H.Lu/HKUST

L1: Course Overview & Review

H.Lu/HKUST L01: RDBMS REVIEW -- 2

The Teaching Staff Instructor: Lu Hongjun

Office: 3543 (Lift 25-26), HKUST E-Mail: [email protected] URL: http://www.cs.ust.hk/~luhj Research Interests:

• Data/Knowledge base management with emphasis on query processing and optimization

• Data warehousing and data mining• Applied performance evaluation• Database application development • Parallel and distributed database systems

TA: Name Jiang Haifeng Liu Guimei Office: 4212 (DB Lab) HKUST E-Mail: [email protected] [email protected] URL: http://ihome.ust.hk/~jianghf http://ihome.ust.hk/~cslgm


References

R.Ramakrishnan & J. Gehrke. Database Management Systems, 3rd Ed. McGraw Hill, 2000

D. Shasha & P. Bonnet. Database Tuning: Principles, Experiments, and Troubleshooting Techniques, Revised edition , Morgan Kaufmann, 2002

Related papers


Course Contents

Part I: Issues in database administration Database design Principles of database performance tuning Database security

Part II: Emerging DB-related technology OLAP and data warehouse XML data management Data stream processing

Course Web Page: http://course.cs.ust.hk/comp334/


Grading

Written assignment (20%) Exams (25%) Course project (50 %) Class participation (5%)


Course Project Requirements Carried in teams of two or four Database related projects

You propose your own project, and get approve from the instructor

Topic: database related The amount of work : it accounts for 50% of your final

grade Required documents (double-spaced)

Project proposal (1-2 pages)• due date: 23-24/02

Status report (4-6 pages)• due date: 28-29/03

Final report (8-10 pages)• due date: 10-11/05


Summary

It is a graduate level course Not a DBA course Not an introductory database course Not a programming course, but you need to know

how to write programs Hopefully, you will leave with

A good grade A good understanding of studied topics


Review -- RDBMS

Relational database systems The basic concepts in database systems Relational data model Relational languages

Database design Previous course: conceptual and logic design This course: physical database design

Database management systems The basic components of DBMS Storage management Transaction management Query processing & optimization


What Is Database & DBMS?

Database: a very large, integrated, persistent collection of data. Models real-world enterprise.

• Entities (e.g., students, courses)

• Relationships (e.g., James is taking CSIT530)

A Database Management System (DBMS) is a software package designed to store and manage databases.


Data Models

A data model is a collection of concepts for describing data and related operations, semantics of data, relationship among data, and constraints on data

Two types of data models Conceptual models: emphasize semantics of data

• Entity-Relationship model, Object-Oriented model

Logical models: ways how the data is organized in the logical level

• Hierarchical model, Network model, Relational model


Instances and Schemas

A schema is a description of a particular collection of data, using a given data model - the logical structure of the database (e.g., set of customers and accounts and the relationship between them)

Schema Instance - the actual content of the database at a particular point in time

Similar to types and variables in programming languages


Levels of Abstraction

ANSI-SPARC three-level architecture

Many views, single conceptual (logical) schema and physical schema. Views describe how users

see the data.

Conceptual schema defines logical structure

Physical schema describes the files and indexes used.

View

Conceptual Schema

Physical Schema

ViewView


Data Independence

Applications insulated from how data is structured and stored. Ability to modify a schema definition in one level without

affecting a schema definition in the next higher level. The interfaces between the various levels and components

should be well defined so that changes in some parts do not seriously influence others.

Logical data independence: Protection from changes in logical structure of data.

Physical data independence: Protection from changes in physical structure of data.


Database Environment

ProceduresAnd standards

Data

DBMS

Hardware

ApplicationPrograms

Systemadministrator

DatabaseAdministrator

Analysts &Programmers

DatabaseDesigner

designs

manages

designs

writeuse

Specifies & enforces

End Users


DBMS Related Languages

Data Definition Language (DDL) Specification notation for defining the database schema Data storage and definition language - special type of

DDL in which the storage structure and access methods used by the database system are specified

Data Manipulation Language (DML) Language for accessing and manipulation the data

organized by the appropriate data model Two classes of languages

• Procedural - user specifies what data is required and how to get those data.

• Nonprocedural - user specifies what data is required without specifying how to get those data


DBMS Related Languages

Programming

Language for

DBMS Applications

Host Language

Data Sublanguage

DDL

DML

Query Language

Procedural

Non-Procedural


Evolution of Database Technology

1960s: Hierarchical (IMS) & network (CODASYL) DBMS.

1970s: Relational data model, relational DBMS implementation.

1980: RDBMS rules the earth 1985-: Advanced data models (extended-relational,

OO, deductive, etc.)

Application-oriented DBMS (spatial, scientific, engineering, etc.).

1990s: ORDB, OLAP, Data mining, data warehousing, multimedia databases, and network databases.


What is an RDBMS

A piece of software that manages data based on the relational model Relational data, SQL queries

Commercial products Oracle, IBM DB2, IBM Informix, Sybase,

Microsoft SQL Server Each has ~10 million lines of C/C++ code

Smaller packages – MySQL, PostgresSQL


Relational Data Model

Main concept: relation A table with rows and columns

Every relation has a schema Description of the columns, or fields

Relational data – rows in a table No order among the rows in a table

The most widely used data model!


University Database

Conceptual schema: Students (sid: string, name: string, login: string, age:

integer, gpa:real)

Cardinality = 3, degree = 5 , all rows distinct Courses (cid: string, cname:string, credits:integer) Enrolled (sid:string, cid:string, grade:string)

sid name login age gpa

53666 Jones jones@cs 18 3.4 53688 Smith smith@eecs 18 3.2 53650 Smith smith@math 19 3.8


Relational Languages

Formal languages Relational algebra Relational calculus

Commercial language: SQL DDL (Data Definition Language)

• Create Table, Create Index, Create View … DML (Data Manipulation Language)

• Queries– Select

• Updates– Insert, Delete, Update


Creating Tables

CREATE TABLE Students

(sid: CHAR(20), name: CHAR(20), login: CHAR(10), age: INTEGER, gpa: REAL)

CREATE TABLE Enrolled

(sid: CHAR(20), cid: CHAR(20), grade: CHAR(2))


Primary Key Constraints

A set of fields is a key for a relation if : 1. Any two distinct tuples differ in some fields of

the set, and 2. This is not true for any subset of the set.

A superkey: Condition 1 true and 2 false. E.g., sid is a key for Students. {sid, gpa} is a

superkey. One primary key can be set per relation.


Primary and Candidate Keys

CREATE TABLE Students

(sid: CHAR(20), name: CHAR(20), login: CHAR(10), age: INTEGER, gpa: REAL,PRIMARY KEY (sid),UNIQUE (login))

CREATE TABLE Enrolled (sid CHAR(20) cid CHAR(20), grade CHAR(2), PRIMARY KEY (sid,cid))


Foreign Key Constraints

Foreign key : a set of fields in a relation Refers to the primary key of another relation

Referential integrity No dangling references

CREATE TABLE Enrolled (sid CHAR(20), cid CHAR(20), grade CHAR(2), PRIMARY KEY (sid,cid), FOREIGN KEY (sid) REFERENCES Students )


53666 Jones jones@cs 18 3.453688 Smith smith@eecs 18 3.253650 Smith smith@math 19 3.8

sid cid grade53666 Carnatic101 C53666 Reggae203 B53650 Topology112 A53666 History105 B

EnrolledStudents


Integrity Constraints (ICs)

IC: condition that must be true for any db instance Domain constraints Primary constraints Foreign key constraints

ICs are specified when a schema is defined. ICs are checked when relations are modified. A legal instance of a relation

Satisfies all specified ICs


Adding and Deleting Tuples

INSERT INTO Students (sid, name, login, age, gpa)VALUES (53688, ‘Smith’, ‘smith@ee’, 18, 3.2)

DELETE FROM Students SWHERE S.name = ‘Smith’


Queries

SELECT *FROM Students SWHERE S.sid = 53688




Querying Multiple Tables

SELECT S.name, E.cidFROM Students S, Enrolled EWHERE S.sid=E.sid AND E.grade=“A”

S.name E.cid

Smith Topology112



sid cid grade53666 Carnatic101 C53666 Reggae203 B53650 Topology112 A53666 History105 B

EnrolledStudents


Functional Components of DBMS

Statistics

Metadata

Indexes

User data

Storage Manager

Buffer Management

Index/file/record

Management

Execution Engine

Query Processing & Optimization

Buffer

DDL Compiler

Transaction Management

Recovery

Log

Concurrency Control

Lock Table

Query Plan

DDL Command

User/Application Database Administrator

Security Control

Storage Management

DML Stmt.

Query Processing

Transaction Manager


Query Optimization

A major strength of RDBMS SQL queries are declarative Optimizer figures out how to answer them

Re-order operations Pick among alternatives of one operation Ensure that the answer is correct!


Transaction

A key concept in databases An atomic sequence of actions (read/write) Brings DB from a consistent state to another ACID

Atomicity Consistency Isolation Durability


Concurrency Control & Recovery

Concurrency Control Essential for good DBMS performance Run several user programs concurrently Interleave actions of different users Ensure the correctness

• Users may think it is a single-user system.

Recovery Essential for durability of transactions


RDBMS Features

Effective and efficient access Easier application development Data independence Data integrity and security Concurrent access Recovery from crashes Uniform data administration


Summary

DBMS used to maintain, query large datasets. Benefits include recovery from system crashes,

concurrent access, quick application development, data integrity and security.

Levels of abstraction give data independence. A DBMS typically has a layered architecture. DBAs hold responsible jobs and are well-paid! DBMS R&D is one of the broadest, most exciting areas in CS.

L1: Course Overview & Review

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