Database Management Systems

Lecture 1 Introduction to Database Systems

Instructor: Li Ma

Department of Computer ScienceTexas Southern University, Houston

August, 2007

04/19/23 by Li Ma, TSU - CS346

Database Systems

•What is a database?– A collection of a large amount of data– Persist over a long periods of time safely– Managed by DBMS

•What is DBMS?– Database Management Systems– A software system– A powerful tool for creating and managing

an database efficiently

04/19/23 by Li Ma, TSU - CS346

Banking System ─ An Example of DBMS

−Data: information on accounts, customers, balance, interest, transaction histories, etc.• Massive: many gigabytes at minimum,

more if keep history of transaction, even more if keep images of checks

• Persistent: data outlives programs that operate on it

04/19/23 by Li Ma, TSU - CS346

Banking System ─ An Example of DBMS (cont)

•Multi-user: many people/programs accessing same database, or even same data simultaneously

•Convenient: simple commands – transfer funds, get balance, etc.

•Efficient: no need to search all files for some specific operation – get balance of one account, etc.

04/19/23 by Li Ma, TSU - CS346

Database Management Systems

•A DBMS provides– Persistent storage– Programming interface (for query processing)– Transaction management (for simultaneous

access)

•Components of a DBMS– The storage manager– The query processor– The transaction manager

04/19/23 by Li Ma, TSU - CS346

Major DBMS vendors/Products

•Oracles

• IBM (DB2)

•Microsoft (SQL server, Access)

• Informix

•Sybase

−All are “relational” or “object-relational” database systems

04/19/23 by Li Ma, TSU - CS346

Terminology

•Data model: describes conceptual structuring of data stored in database– Ex. Data is a set of records, each with

student ID, name, address, courses, photo

– Ex. Data is graph where nodes represent cities, edges represent airline routes

04/19/23 by Li Ma, TSU - CS346

Terminology (cont)

•Schema vs. Data– Data is actual “instance” of database,

changes rapidly– Schema describes how data is to be

structured, defined at set-up time, specified in one of the languages, rarely changes - metadata

– Like types vs. variables in programming language

04/19/23 by Li Ma, TSU - CS346

Terminology (cont)

•Data Definition Language (DDL)– Commands for setting up schema of

database– Process of designing schema can be

complex, may use design methodology and/or tool

04/19/23 by Li Ma, TSU - CS346

Terminology (cont)

•Data Manipulation Language (DML)– Commands for manipulating data in

database•Retrieve, insert, delete, modify

– It is also called “query language”•Queries could be expressed in a very high-

level language, which greatly increased the efficiency of database programming

04/19/23 by Li Ma, TSU - CS346

Terminology (cont)

•People– DBMS implementers: build system– Database designers: set up schema,

load data– Database users: query/modify data

04/19/23 by Li Ma, TSU - CS346

Content of This Course

• Design of Database: how to develop a useful database?– E/R model (Chapter 2)– Relational model (Chapter 3)

• Database programming: how to express queries on the database?– Relational algebra (Chapter 5)– SQL (Chapter 6&7)

• Not DBMS implementation