Database Management Systems Lecture # 01 Instructor: Engr. Sana Ziafat

Introduction: What Is Database? A very large, integrated collection of data. Database: An organized collection of logically related data.

Types of Databases and Database Applications Numeric and Textual Databases Multimedia Databases Geographic Information Systems (GIS) Data Warehouses

Definitions Data: Meaningful facts, text, graphics, images, sound, video segments Information: Data processed to be useful in decision making Metadata: Data that describes data

Figure: Data in Context

Figure: Summarized data Useful information that managers can use for decision making and interpretation

Table: Metadata Descriptions of the properties or characteristics of the data, including data types, field sizes, allowable values, and documentation

What is DBMS A Database Management System (DBMS) is a software package designed to store and manage databases. A DBMS is a data storage and retrieval system which permits data to be stored non-redundantly while making it appear to the user as if the data is well-integrated.

Database Management System DBMS Database containing centralized shared data Application #1 #2 #3 DBMS manages data resources like an operating system manages hardware resources

A simplified database system environment

Typical DBMS Functionality Define a database : in terms of data types, structures and constraints Construct or Load the Database on a secondary storage medium Manipulating the database : querying, generating reports, insertions, deletions and modifications to its content Concurrent Processing and Sharing by a set of users and programs – yet, keeping all data valid and consistent

Typical DBMS Functionality Other features: Protection or Security measures to prevent unauthorized access “Active” processing to take internal actions on data Presentation and Visualization of data

Example Mini-world for the example: Part of a UNIVERSITY environment. Some mini-world entities: - STUDENTs - COURSEs - SECTIONs (of COURSEs) - (academic) DEPARTMENTs - INSTRUCTORs Some mini-world relationships: - SECTIONs are of specific COURSEs - STUDENTs take SECTIONs - COURSEs have prerequisite COURSEs - INSTRUCTORs teach SECTIONs - COURSEs are offered by DEPARTMENTs - STUDENTs major in DEPARTMENTs

Define UNIVERSITY database Structure of the record STUDENT ( Name , Number, Class, Major) COURSE ( Name , Number, Credit, Dept.) Data type of data element Name: a string of characters Number: integer Grade: {A,B,C,D,F,I} ….. Constraints The sections that students take must be taught by some instructors.

Construct UNIVERSITY database Store data on storage medium -store data for each student, course, section, grade repot, prerequisite records in various files may be related to one another Manipulate UNIVERSITY database Query: Retrieve the transcript ( a list of all courses and grades) of Smith. Update: Create a new section for the database course for this semester.

Disadvantages of File Processing Program-Data Dependence All programs maintain metadata for each file they use Data Redundancy (Duplication of data) Different systems/programs have separate copies of the same data Limited Data Sharing No centralized control of data Lengthy Development Times Programmers must design their own file formats Excessive Program Maintenance 80% of of information systems budget

Figure: Three file processing systems at Pine Valley Furniture Duplicate Data

Problems with Data Dependency Each application programmer must maintain their own data Each application program needs to include code for the metadata of each file Each application program must have its own processing routines for reading, inserting, updating and deleting data Lack of coordination and central control Non-standard file formats

Problems with Data Redundancy Waste of space to have duplicate data Causes more maintenance headaches The biggest Problem: When data changes in one file, could cause inconsistencies Compromises data integrity

SOLUTION: The DATABASE Approach Central repository of shared data Data is managed by a controlling agent Stored in a standardized, convenient form Requires a Database Management System (DBMS)

Advantages of Database Approach Program-Data Independence Metadata stored in DBMS, so applications don’t need to worry about data formats Data queries/updates managed by DBMS so programs don’t need to process data access routines Results in: increased application development and maintenance productivity Minimal Data Redundancy Leads to increased data integrity/consistency

Advantages of Database Approach Improved Data Sharing Different users get different views of the data Enforcement of Standards All data access is done in the same way Improved Data Quality Constraints, data validation rules Better Data Accessibility/ Responsiveness Use of standard data query language (SQL) Security, Backup/Recovery, Concurrency Disaster recovery is easier

Costs and Risks of the Database Approach Up-front costs: Installation Management Cost and Complexity Conversion Costs Ongoing Costs Requires New, Specialized Personnel Need for Explicit Backup and Recovery Organizational Conflict Old habits die hard

Conversion to database approach Step 1: Enterprise Data model: Graphical model that shows high level entities for organization and associations among these entities. Step 2: Relational Data Model: Defining tables for each entity. Step 3: Implement

Continued.. A data model is a collection of concepts for describing data. A schema is a description of a particular collection of data, using the a given data model. The relational model of data is the most widely used model today. - Main concept: relation, basically a table with rows and columns. - Every relation has a schema, which describes the columns, or fields

Segment from enterprise data model

One customer may place many orders, but each order is placed by a single customer  One-to-many relationship

Therefore, one order involves many products and one product is involved in many orders  Many-to-many relationship

Database Users Users may be divided into those who actually use and control the content (called “Actors on the Scene”) and those who enable the database to be developed and the DBMS software to be designed and implemented (called “Workers Behind the Scene”).

Database Users Actors on the scene Database administrators: responsible for authorizing access to the database, for co-ordinating and monitoring its use, acquiring software, and hardware resources, controlling its use and monitoring efficiency of operations. Database Designers: responsible to define the content, the structure, the constraints, and functions or transactions against the database. They must communicate with the end-users and understand their needs. End-users: they use the data for queries, reports and some of them actually update the database content.

Categories of End users Sophisticated Users: these include business analysts, scientists, engineers, others thoroughly familiar with the system capabilities. Many use tools in the form of software packages that work closely with the stored database. Naive Users: They don’t need to know any details of structure. They access the database by writing simple commands or by choosing operations from menus.

Workers behind the scene Persons whose job involves design, development, operation,and maintenance of the DBMS software and system environment. DBMS designers and implementers: Design and implement the DBMS software package itself. Tool developers: Design and implement tools that facilitate the use of the DBMS software. Tools include design tools, performance tools, special interfaces,etc. Operators and maintenance personnel: Work on running and maintaining the hardware and software environment for the database system.

Figure Client/server system

The Range of Database Applications Personal Database – standalone desktop database Workgroup Database – local area network (<25 users) Department Database – local area network (25-100 users) Enterprise Database – wide-area network (hundreds or thousands of users)

Figure: Typical data from a personal computer database

Figure: Workgroup database with local area network

Figure : An enterprise data warehouse

Figure: Components of the database environment

Evolution of DB Systems Flat files - 1960s - 1980s Hierarchical – 1970s - 1990s Network – 1970s - 1990s Relational – 1980s - present Object-oriented – 1990s - present Object-relational – 1990s - present Data warehousing – 1980s - present Web-enabled – 1990s - present

When not to use DBMS Main costs of using a DBMS: - High initial investment in hardware, software,training and possible need for additional hardware. - Overhead for providing generality, security, recovery, integrity, and concurrency control. - Generality that a DBMS provides for defining and processing data. When a DBMS may be unnecessary: - If the database and applications are simple, well defined, and not expected to change. - If there are stringent real-time requirements that may not be met because of DBMS overhead. - If access to data by multiple users is not required.

Quick Review CASE Tools – computer-aided software engineering Repository – centralized storehouse of metadata Database Management System (DBMS) – software for managing the database Database – storehouse of the data Application Programs – software using the data User Interface – text and graphical displays to users Data Administrators – personnel responsible for maintaining the database System Developers – personnel responsible for designing databases and software End Users – people who use the applications and databases

????? Indicate whether there is one-to-many or many-to-many relationships? STUDENT and COURSE( student registers for course) BOOK and BOOK COPY (books have copies) INSTRUCTOR and COURSE