Client/Server Databases and the Oracle 10g Relational Database Chapter 1: Client/Server Databases and the Oracle 10g Relational Database Guide to Oracle 10g

Objectives Develop an understanding of the purpose of database systems Describe the purpose and contents of an entity-relationship model Explain the steps in the normalization process Describe the differences between personal and client/server databases Guide to Oracle 10g

Introduction If an organization needs to store and maintain a large amount of data that must be viewed and updated by many users at the same time, it often uses a client/server database such as Oracle 11g. Guide to Oracle 10g

Database Systems Data files consist of: Fields Records Describe characteristics Also called columns Records Group of related fields Guide to Oracle 10g

Database Systems (continued) Problems with storing data in files: Proliferation of data management programs Presence of redundant data Inconsistent data Database Stores all organizational data in central location Eliminates redundant data to reduce possibility of inconsistent data Guide to Oracle 10g

Database Systems (continued) Database management system (DBMS) Application that performs all routine data-handling operations Provides central set of common functions for managing database Inserting Updating Retrieving Deleting data values Guide to Oracle 10g

Database Approach to Data Processing Guide to Oracle 10g

Database Systems (continued) Database administrator Person responsible for installing, administering, and maintaining the database Often called DBA Guide to Oracle 10g

Overview of Relational Databases Table Matrix with columns and rows Columns Represent different data fields Characteristics or attributes about entity Rows Contain individual records Attributes about a specific instance of entity Guide to Oracle 10g

Overview of Relational Databases (continued) Guide to Oracle 10g

Overview of Relational Databases (continued) Entity Object about which you want to store data Different tables store data about each different entity Relationships Links that show how different records are related Guide to Oracle 10g

Overview of Relational Databases (continued) Key fields Establish relationships among records in different tables Main types of key fields Primary Candidate Surrogate Foreign Composite Guide to Oracle 10g

Primary Keys Column in relational database table whose value must be unique for each row Serves to identify individual occurrence of entity Every row must have a primary key Cannot be NULL NULL Value is absent or unknown No entry is made for that data element Guide to Oracle 10g

Candidate Keys Any column that could be used as the primary key Should be a column that is unique for each record and does not change Guide to Oracle 10g

Surrogate Keys Column created to be record’s primary key identifier Has no real relationship to row to which it is assigned other than to identify it uniquely Surrogate key values automatically generated using a sequence Guide to Oracle 10g

Foreign Keys Column in table that is a primary key in another table Creates relationship between two tables Value must exist in table where it is the primary key Guide to Oracle 10g

Composite Keys Unique key that is created by combining two or more columns Usually comprises fields that are primary keys in other tables Composite Key ORDER_ID PRODUCT_ID ORDER_QUANTITY 100 1 2 200 Guide to Oracle 10g

Database Systems Consists of Server DBMS Database applications Manages physical storage and data retrieval Database applications Provide interface that allows users to interact with database Server Computer that shares resources with other computers Guide to Oracle 10g

Database Systems (continued) Server process Program that listens for requests for resources from clients Responds to requests Client Program that requests and uses server resources Guide to Oracle 10g

Client/Server Database Management Systems DBMS server process runs on one workstation Database applications run on separate client workstations across network Server sends only requested data back to client rather than entire database Guide to Oracle 10g

Client/Server Database Architecture Guide to Oracle 10g

Client/Server Database Management Systems (continued) Generate less network traffic than personal databases Extra features to minimize chance of failure Powerful recovery mechanisms that often operate automatically Maintain file-based transaction log on database server Guide to Oracle 10g

Client/Server Database Management Systems (continued) Preferred for Database applications that retrieve and manipulate small amounts of data from databases containing large numbers of records Mission-critical applications Web-based database applications that require increased security and fault tolerance Guide to Oracle 10g

The Oracle 10g Client/Server Database Latest release of Oracle Corporation’s relational database Client/server database Server side DBMS server process Oracle Net Utility that enables network communication between client and server Guide to Oracle 10g

Client/Server Architecture for Oracle 10g DBMS Guide to Oracle 10g

The Oracle 10g Client/Server Database (continued) Oracle Application Server Used to create World Wide Web pages that allow users to access Oracle databases Oracle client products: SQL*Plus Oracle 10g Developer Suite Enterprise Manager Guide to Oracle 10g