This document provides an overview of key concepts in database management systems including: 1. It discusses different data models including relational, entity-relationship, and object-oriented models. 2. It describes database system components like data definition language, data manipulation language, and transaction management. 3. It outlines different types of users that interact with database systems and roles like database administrators.

1. CS157A Lecture 2 DB Mangement Systems Prof. Sin-Min Lee Department of Computer Science San Jose State University

8. DATABASE AND DBMS CONCEPTS Database – is a collection of data, typically describing the activities of one or more related organizations. A Database Management System DBMS) is software designed to assist in maintaining and utilization large collections of data. The SQL (Structured Query Language), developed by IBM is now the standard query language.

13. Example of an Instance of Students Students Schema ------> Students (sid : String, Age : Integer) 35 53-688 28 53-666 Age Sid

22. In the the past as new applications were written they used existing files, or created a new file for their use. Sometimes several existing files need to be sorted and merged to obtain the new file.Thus, it is probable that several files will contain the same information stored in different ways. In other words, there will be redundant and possibly inconsistent data. Consider the files for an insurance company Traditional File Systems POLICY# POLICYHOLDER PREMIUMS data ADDRESS PREMIUM-PA PREMIUM-TOTAL POLICY# POLICYHOLDER AGENCY data ADDRESS AGENT-CODE RENEWAL-DATE RENEWAL-AMT

24. Basic Definitions Database: A collection of related data Data: Known facts that can be recorded Schema: Some part of the real world about which data is stored in the database. Database Management System(DBMS): A software package to facilitate the creation and maintenance of a computerised database.

28. Three Schema Architecture External Schema 1 External Schema 2 External Schema n Conceptual Schema Internal Schema

33. Inter-Related Data CLAIMS RENEWALS AGENCY D B M S RENEWALS CLAIMS AGENCY QUERY Data related by structure Flexible enquiry easier

34. Multiple Applications CLAIMS AGENCY DATABASE LOCAL VIEWS RENEWALS

39. View of Data An architecture for a database system

45. A Sample Relational Database

53. Overall System Structure