LiaoNing ShiHua University Database Principles LiaoNing ShiHua University

Textbooks Required: Recommended: You may also want: A First Course in Database Systems,2nd, by Jeffrey D.Ullman Jennifer Widom. Recommended: 王珊,萨师煊. 数据库系统概论(第四版). 高等教育出版社, 2006 年 Books on SQL Server 2000 or 2005 You may also want: Books on design and programming : Powerbuilder, PowerDesigner, UML, VB, Delphi, VC, JAVA, C#, ASP, PHP, JSP etc.

Why Using English Textbook ? More computer English words More advanced and newest information Better information retrieval capability More international communication chance

What to learn in this unit ? Basic theories (basic) System and database design (designer) Application Programming (programmer) Database management and maintenance (database manager)

Syllabus Background and history of database management systems Fundamentals of using a database management systems: SQL Server2000. Database modeling Relational model: theoretical background and operations Database Language SQL Fundamentals of database management systems: transactions and security etc. Database system design and practice

Chapter 1 The Worlds of Database Systems Evolution of Database Systems Architecture of DBMS and DBS Future of Database Systems

1.1 Evolution of Database Systems 1.1.1 Some Basic notions Data Database (DB) Database Management System (DBMS) Database System (DBS). Database Administrator (DBA)

Basic Notions Data Database (DB) Distinct pieces of information represented in a form suitable for processing by computer. Data can exist in a variety of forms -- as digital numbers, text, image, sound, video and etc. Database (DB) In essence, it’s nothing more than a collection of information that exists over a long period of time. In common parlance, it refers to a collection of data managed by a database management system (DBMS) or just database system (DBS).

Example of Data and Database

Another example: University Database Students Sid Sname Ssex Sage sdept 0121001 Tom M 21 Cs 0121002 Mary F 20 0121025 Jack 18 0110033 Smith 19 Ma 0211010 Alane 22 Is Courses Enrolled cid Cname credit 1 Programming 4 2 English 6 3 Physics Dbms sid cid grade 0121002 4 92 3 88 0110033 1 70 0211010 85 2 95

DBMS Database Management System (DBMS) A collection of programs that enables you to store, modify, and extract information from a database. There are many different types of DBMSs, ranging from small systems that run on personal computers to huge systems that run on mainframes.

Basic functions of DBMS Data definition Allow creating new databases and specify their schema (logical structure of the data), via data definition language (DDL). Data manipulation Allow efficient access to the data, such as querying and modifying the data, via query language or data manipulation language (DML). Operation management of DB Support the storage of very large amounts of data over a long period of time, assuring data integrity, keeping data secure from accident or unauthorized use. Support concurrent, atomic access to data. Creation and maintenance of DB Such as inputting and transferring of Data, DB backup and recovery, performance monitoring, audit and analysis etc.

Database System (DBS) Database System (DBS). User Application Systems DB, DBMS, Development Tools, DB applications, DB Administrator (DBA) and users DB OS DBMS Developing Tools DB applications User DBA Hardware Operating System DBMS, Compiling System Developing Tools Application Systems DBMS in Computer System

Database Administrator DBA Person who is responsible for management and maintenance of DB. Tasks Database contents and structures Storage structure and access methods Database security and integration Monitor and improve database performance

1.1.2 History of Data management File systems Problems: limited support to definition of data schema, no directly support to DML (Data Manipulate Language), no support to efficient concurrent, secure access etc. Early DBMS The first commercial DBMS appeared in the late 1960’s, evolved from file systems. The early DBMS’s used several data models for describing structure of DB: hierarchical model and network model. Problems: no support to high-level query languages.

History of Data management (cont.） Relational DBMS A famous paper by Ted Codd in 1970, “A relational model for large shared data banks” in Comm. ACM. Data organized as tables called relations. Unlike the user of early DBS, user of a relational system won’t be concerned with the storage structure, and queries are expressed in a very high-level language (SQL). Today used in most DBMS's.

Relational Model Attributes (column headers) Tuples (rows) Based on tables, such as: Attributes (column headers) acct # name balance 12345 Sally 1000.21 34567 Sue 285.48 … Tuples (rows)

Query Languages Employee Name Dept Department Manager SELECT Manager FROM Employee, Department WHERE Employee.name = "Clark Kent” AND Employee.Dept = Department.Dept ;

History of Data Model Hierarchical model 60’s 70's 80's 90’s now abstraction of data features in real world into computer world. Hierarchical model 60’s 70's 80's 90’s now Relational model Choice for most new applications Object Bases model Knowledge Bases model Network model

Relational model or not? Relational model is good for: Large amounts of data —> simple operations Navigate among small number of relations Difficult Applications for relational model: VLSI Design (CAD in general) CASE: Computer-Aided Software Engineering Graphical Data Where number of "relations" is large, relationships are complex Object Data Model Logic Data Model

Other Data Models Object data model Logic data model Usually find objects via explicit navigation, also query language in some systems Complex Objects – Nested Structure (pointers or references) Encapsulation, set of Methods/Access functions Object Identity Inheritance – Defining new classes like old classes Logic data model Prolog, Datalog More power than relational

The DBMS Marketplace Relational DBMS companies – Oracle, Sybase – are among the largest software companies in the world. IBM offers its relational DB2 system. With IMS, a nonrelational system, IBM is by some accounts the largest DBMS vendor in the world. Microsoft offers SQL-Server, plus Microsoft Access for the cheap DBMS on the desktop, answered by “lite” systems from other competitors. Relational companies also challenged by “object-oriented DB” companies. But countered with “object-relational” systems, which retain the relational core while allowing type extension as in OO systems.

1.2 Architecture of DBMS Major components of a DBMS Schema Queries Data Metadata Storage Manager Query Processor Transaction Manager Schema Modifications Queries Schema (logical structure of the data); Metadata(data of data)

Architecture of DBS Three Schema Architecture of DBS External Schema: user schema or subschema Defines one view of the data as seen by a specific set of application or end users. There may be many external schemas in a DB. Schema: conceptual schema, logical schema Defines data from perspective systems designer; Independent of end users & data storage mechanism There is only one conceptual schema in a DB. Internal Schema: storage schema Defines how data is organized, stored and manipulated inside the system. Totally dependent on particular implementation. There is only one internal schema in a DB.

Three Schema Architecture (cont.) Application A External Schema 1 Schema Internal DB B D E C External Schema 2 External Schema 3

Independence of Data and Program Logical Independence Via Reflection of External Schema/Schema One Schema corresponds to many External schemas; every Ex-Schema has an Ex-Schema/Schema Reflection. When Schema changes, DBA changes the Ex-Schema/Schema reflections, so application programs needn’t been changed. Physical Independence Via Reflection of Schema/Internal Schema Schema/Internal Schema Reflection is unique. When Internal Schema changes, DBA changes the Schema/ Internal Schema Reflection, so application programs needn’t been changed.

Three Aspects to Studying DBMS's Modeling and design of databases Allows exploration of issues before committing to an implementation. Application programming SQL: queries and DB operations like update. Host language and Embedded SQL DBMS implementation Storage, query processing, transaction, …