Database Design Chapter-1- Basic Concepts Reference: Prof. Mona Mursi Lecture notes Dr.Lilac Safadi Lecture notes Feb 26,2008 Fatimah Alakeel

Database Concepts Data is a meaningless static value. What does 3421 means? Information is the data you process in a manner that makes it meaningful. Information can be provided only if proper data exists. A database (DB) is a collection of related persistent data. Can be generated & maintained manually or automatically Data is what you store in database. Information is what you retrieve from a database. A database application is a collection of data and the programs that allow the manipulation of these data to meet the information needs of an enterprise Feb 26,2008 Fatimah Alakeel

Database Application: Examples KSU Library Saudia Airline Reservations Car rental DB A DB for all schools in Riyadh   Feb 26,2008 Fatimah Alakeel

Database Properties Represents the real world (miniworld, Universe of Discourse UoD) Logically coherent collection of data. Designed, built, populated with data for a specific purpose. It has an intended group of users and their applications. Can be of any size and any degree of complexity. Can be generated and maintained manually or using a computer. A computerized DB can be created by: A Group of application programs Or by Database Management System (DBMS) Feb 26,2008 Fatimah Alakeel

The Data in the DB are Shared by multiple users Stored less redundantly Made independent of applications Organized Feb 26,2008 Fatimah Alakeel

Database Management System (DBMS) A collection of programs that enables the users to create and maintain a database. A general- purpose software system that facilitates the process of : Defining (specifying data types, structures and constraints) Constructing (storing the data on a storage medium controlled by DBMS) Manipulating (querying, update, generate reports) And Maintaining The database for various applications . Feb 26,2008 Fatimah Alakeel

DBS Environment DBS Application Programs DBMS Query Process Data Access Meta-Data Database Database System = Database + DBMS Feb 26,2008 Fatimah Alakeel

DBMS Capabilities & Responsibilities Control redundancy. Access a large amount of data efficiently. Support a data model in which is conceptually captured. Support HLL to define, access and manipulate data. Provide correct access to data by multiple users. Provide multiple users views. Maintain data integrity. Protect data. Recover from failures. Feb 26,2008 Fatimah Alakeel

Database Management System Major Relational DBMS vendors/products Paradox by Corel dBase, Clipper FoxPro, Access & SQL Server by MS MySQL DB2 by IBM Oracle, Sybase, Informix Feb 26,2008 Fatimah Alakeel

Advantages of Database Systems over Paper-Based Systems Compactness Speed Less of hard work Currency Feb 26,2008 Fatimah Alakeel

File-Based Systems (FBS) FBS is a collection of application programs that perform tasks where each program defines and manages its own data. File handling Data Entry User 1 File Def Application Program 1 File1 File handling Data Entry User 2 File Def Application Program 2 File 2 Feb 26,2008 Fatimah Alakeel

File-Based Systems (FBS) The limitations of the FBS approach attributed to two factors: The definition of data is embedded in the application programs There is no control over the access & manipulation of data beyond the imposed by the application program Feb 26,2008 Fatimah Alakeel

Differences between Files and a database A database is self contained A database contains the description (system catalog OR data dictionary OR meta data). Feb 26,2008 Fatimah Alakeel

File-Based Systems (FBS) Disadvantages Data Redundancy & Inconsistency Waste of space Cost of update Risk of inconsistency Concurrent Access Anomalies Security Problems Integrity Problems Logical Data Dependence Limited data sharing Inflexibility to access data Poor enforcement of standards Physical Data Dependence Low programmer productivity Excessive program maintenance Feb 26,2008 Fatimah Alakeel

Database Systems Advantages Minimal Data Redundancy Logical Data Dependence Data sharing Multiple access path to data User views Physical Data Dependence Application development is easy Less maintenance Good performance Uniform control for security, privacy and integrity. Feb 26,2008 Fatimah Alakeel

Database Systems Advantages 5- Potential for enforcing standards DBA enforce standards for names and formats of data, display formats, reports structures. 6- Reduced application development time Ex: Retrieval of data or printing a new report 7- Flexibility Change the structure without affecting the data and application programs 8- Up-to-date information is available All users access the DB. Once they save the changes the DB id available to the other users 9- Economies of scale DBMS permits unification of data and application => reduce the cost of operation and management Feb 26,2008 Fatimah Alakeel

Database Systems (DBS) DBS is a single large repository of data, defined once & used by many application programs. Data Entry User 1 Application Program 1 DBMS Data Entry Database User 2 Application Program 2 Feb 26,2008 Fatimah Alakeel

Characteristics of DB Approach Self –Describing nature of a database system The database system contains: Database Complete definition of the DB structure and constraints (catalog) DBMS Meta- Data Database Catalog The DBMS works with any number of database applications Feb 26,2008 Fatimah Alakeel

Characteristics of DB Approach Program-Data Independence In file based systems the structure of data files is embedded in the access programs => any change to the structure may require changing all accessing programs In DBMS any change in the structure does not require changing the access programs because the structure is stored in the DBMS catalog. => this is called program-data independence. Feb 26,2008 Fatimah Alakeel

Characteristics of DB Approach Data Abstraction DBMS provides a conceptual representation of the data => no much details about how the data is stored and how the operations are implemented. There are different levels of abstraction. Feb 26,2008 Fatimah Alakeel

Characteristics of DB Approach Describe some parts of the databse Users Data Abstraction View 1 View 2 View 3 View N …….. Conceptual Level What data is stored and how its interrelated (tables or tree) Database Administrators How the data is stored in the physical media (files of records or structs) Implementers Physical Level Feb 26,2008 Fatimah Alakeel

Data Models Data Model is a set of concepts for describing the structure of a DB (data, relationships, constraints) Used for the conceptual and view levels Categories of data models: - Object-based conceptual model - Record-based logical model - Physical model Feb 26,2008 Fatimah Alakeel

Categories of Data Models Object-based conceptual model The structure of the database is flexible Data constraints specified explicitly Examples: Entity Relationship Model (ER) Object Oriented Models (OO) Characteristics: Entities represent things in the real world Entities are distinct New kind of entities can be constructed from old kinds Feb 26,2008 Fatimah Alakeel

Categories of Data Models Record-based logical model Data viewed as a fixed- format records of various types. Examples: Relational model Network model Hierarchical model Feb 26,2008 Fatimah Alakeel

Data Models Relational Model Network Model Staff_No LName Salary Brn_No Brn_No Street Tel_No Relational Model St1 Name1 7000 1 1 Olayaa 4630000 2 Malaz 4780000 3 Rawda 2310000 St2 Name2 4000 1 St3 Name3 6500 2 St4 Name4 3000 3 St1 Name1 7000 Olayaa 4630000 Malaz 4780000 Network Model St2 Name2 4000 Rawda 2310000 St3 Name3 6500 St4 Name4 3000 Feb 26,2008 Fatimah Alakeel

Data Models Hierarchical Model Malaz 4780000 Olayaa 4630000 Rawda 2310000 St4 Name4 3000 St3 Name3 6500 St1 Name1 7000 St2 Name2 4000 Hierarchical Model Feb 26,2008 Fatimah Alakeel

Database Systems (DBS) Virtual data derived from the data base View 1 View 2 Staff_No FName LName Age Salary Staff_No LName Bno Staff_No FName LName DOB Salary Bno DBS Support of Multiple Views of Data Feb 26,2008 Fatimah Alakeel

Database Systems (DBS) Sharing of data and multiuser transaction processing DBMS includes concurrency control software => to ensure that several users trying to update the same data can do that in a controlled manner so the result of the update is correct. Feb 26,2008 Fatimah Alakeel

Actors in the Scene Database Administrator (DBA): administrates the DB, DBMS & related software Database Designer: Identify the data & choose the appropriate structure to represent & store the data Database user: Queries/modifies data - Naïve users: invoke one of the permanent application programs that have been written previously - Sophisticated users: form requests in a database query language Feb 26,2008 Fatimah Alakeel

Actors in the Scene System Analyst: determine the requirements of end users & develop system specifications Application Programmer: implement system specifications DBMS designer & Implementers Tool Developer Operators & Maintenance Personnel Feb 26,2008 Fatimah Alakeel

DBS Environment User Procedure Requirement DB Designer System Analyst Communicate Procedure User Requirement Write Write DB Designer System Analyst Application programmer Design DBA Program Manage App Program DBMS Use Naïve End User DB Use Sophisticated End User H/W Feb 26,2008 Fatimah Alakeel

When Not to Use a DBMS High initial investment in H/W, S/W and training. Generality provided by DBMS for defining and processing data. Overhead for providing security, concurrency control, recovery and integrity functions. Database & applications are simple, well defined, not expected to change. Real-time requirements can not be met because of overhead. Multiple-user access to data is not required. Feb 26,2008 Fatimah Alakeel

Chapter’s Summery Definition of ( Data, Information ,Database, Database application). Properties of (database, data stored in the database). DBMS definition, properties and responsibilities. File based system vs. database system Database system characteristics. Data models Actors in the scene. When not to use a DBMS. Feb 26,2008 Fatimah Alakeel