1 DATABASE TECHNOLOGIES BUS Abdou Illia, Fall 2007 (Week 3, Tuesday 9/4/2007)

2 LEARNING GOALS  Explain basic concepts of data management.  Describe file systems and identify their problems.  Define database management systems and describe their various functions.  Explain how the relational database model works.  Describe how databases are developed.

3 Basic Concepts of Data Management Database: Collection of data organized in different containers Table 1Table 2Table 3 Report Form 1 Acc #:_______ Name:_______

4 Basic Concepts of Data Management  Table Two-dimensional structure composed of rows and columns  Field Like a column in a spreadsheet  Field name Like a column name in a spreadsheet Examples: AccountID, Customer, Type, Balance  Field values Actual data for the field  Record Set of fields that describe an entity (a person, an account, etc.)  Primary key A field, or group of fields, that uniquely identifies a record AccountIDCustomerTypeBalance John SmithChecking$ Linda MartinSaving$ Paul GrahamChecking$ Accounts table Each table has:  Fields  Records  1 Primary key

5 Basic Concepts in Data Management  A Primary key could be a single field like in this table  A Primary key could be a composite key, i.e. multiple fields

6 Traditional File Systems  System of files that store groups of records used by a particular software application  Simple but with a cost Inability to share data Inadequate security Difficulties in maintenance and expansion Allows data duplication (e.g. redundancy) Application 1 Program 1 File 1 File 2 File 3 Program 2 File 1 File 2 File 3 Application 2 Program 1 File 1 File 2 File 3 Program 2 File 1 File 2 File 3

7 File System Anomalies  Insertion anomaly Data needs to be entered more than once if located in multiple file systems  Modification anomaly Redundant data in separate file systems Inconsistent data in your system  Deletion anomaly Failure to simultaneously delete all copies of redundant data Deletion of critical data

8 Database Management System (DBMS)  Combination of software and data for Collecting, storing and managing data in a database environment.  A DBMS includes: Database Database engine (for accessing and modifying the DB content) Data Manipulation Language Application 1 Program-1 Program-2 Application 2 Program-1 Program-2 DBMS

9 DBMS Functions  Store data (in tables) on secondary storage  Transform data into information (reports,..)  Provide user with different logical views of actual database content  Provide security DBMSs control who can add, view, change, or delete data in the database ID Name Amt 01 John Linda Paul Physical view ID Name 02 Linda Name Amt Paul ID Name Amt 01 John Linda 3.00 Logical views

10 More DBMS Functions  Allow multi-user access Control concurrency of access to data Prevent one user from accessing data that has not been completely updated  When selling tickets online, Ticketmaster allows you to hold a ticket for only 2 minutes to make your purchase decision, then the ticket is released to sell to someone else – that is concurrency control

11 Types of DBMSs  Desktop Used by individuals or small groups Requires little or no formal training Does not have all the capabilities of larger DBMSs

12 Types of DBMSs (Continued)  Enterprise Serve multiple locations and store large amounts of data Either centralized or distributed  Centralized – all data on one server  Easy to maintain  Prone to run slowly when many simultaneous users  No access if the one server goes down  Distributed – each location has part of the database  Very complex database administration  Usually faster than centralized  If one server crashes, others can still continue to operate.

13 Database Models  Database model = a representation of the relationship between structures (e.g. tables) in a database  Four common database models Flat file model Hierarchical, or tree structure, model Network model Relational model (this one is the most common)

14 Flat File Database  Stores data in basic table structures  No relationship between tables  Used on PDAs for address book

15 Hierarchical Database Model  Resembles an inverted tree, with the root at the top  Limited to storing data in one-to-many relationships One parent segment to many child segments  Very fast when searching large amounts of data in a pre-specified order  Not very flexible

16 Network Model  Many-to-many relationships between tables  Any record may be linked to any other record  Highly flexible but also highly complex  Rarely used

17 Relational Model  Multiple tables related by common fields  Uses controlled redundancy to create fields that provide linkage relationships between tables in the database These fields are called foreign keys – the secret to a relational database A foreign key is a field, or group of fields, in one table that is the primary key of another table  Somewhat slower than hierarchical and network DBMSs

18 Database Development 1)Analysis Develop a clear understanding of how the organization works and what data is used Determine data needs of each functional area Analyze data needs and use Develop conceptual model Develop physical model Implement database Administer database

19 Database Development Process (Continued) 2)Develop a conceptual model – Show how data are grouped together and related to each other Entity-Relationship diagrams (ERDs) are used Less expensive to correct an ERD than to redesign an already constructed database

20 Database Development Process (Continued) 3)Develop a physical model – Physical model provides specific details about each table and field in the database Normalization used to remove redundant data and therefore minimize any anomalies Optimize the database for performance

21 Database Development Process (Continued) 4)Database implementation Install the DBMS software Build the database Test

22 Database Development Process (Continued) 5)Database administration Ensures database efficiency Manages backup and restoration Sets up user accounts and security

23 Summary Questions Notes 1)What is a table, a field, a record, a primary key, a composite key? 4-5 2) What are the problems with traditional file systems? 6,7 3) What are the major components of a DBMS? 8 4)(a) Name some Desktop DBMSs. (b) Name some Enterprise DBMSs. 5)What are the differences between Flat File and Relational database models? 14,17 6)What are the steps for Database development? 18-