HND Agri DBMS Introduction MH Mohamed Nafas 1

Why DBMS? 2  Suppose we need to develop a Information system.  How do we  store the data? (use file structures…)  query the data? (write programs…)  Update data safely? (write more programs…)  provide different views on the same data? (staff & students diffrent) ( prog…)  deal with crashes? (prog…)  DBMS helps to above activities.

File based system 3  Manual file Processing (paper based)  Time Consuming  Does not support large volumes of data  File based Processing  Database Management system

Library System Files File Based Processing 4 Data Entry File Processing Data Entry File Processing ID001 Namemery Addresscolombo TelNo Marks34 ID001 Namemery Addresscolombo TelNo Books-bor 6 Student System Files Data Duplication

Library System Files File Based Processing 5 Data Entry File Processing Data Entry File Processing ID001 Namemery Addresscolombo TelNo Marks34 ID001 Namemery Addresscolombo TelNo Books-bor 6 Student System Files Change request

Library System Files File Based Processing 6 Data Entry File Processing Data Entry File Processing ID001 Namemery AddressKandy TelNo Marks34 ID001 Namemery Addresscolombo TelNo Books-bor 6 Student System Files Inconsistent Data Address Change request

Problem in file based system 7  Inconsistent data  Data duplication  Security  Inflexibility  Limited data sharing  Excessive program maintenance  How do we resolve these problems?

Solution is DBMS 8  DBMS is solution to rectify file based processing problems

Data Entry & Reports Data Entry & Reports DBMS Students Library Application Programs App. Programs Database Database Processing stno Name address 001 mery colombo ……………. Change Request

Data Entry & Reports Data Entry & Reports DBMS Students Library Application Programs App. Programs Database Database Processing stno Name address 001 mery Kandy ……………. Change Request

DATABASE 11 DEFINITION  A shared collection of logically related data designed to meet the information requirements of an organisation.

Database Management System (DBMS) 12  A software system that enables users to define, create and maintain the database and which provides controlled access to the database.

History of Database Systems 13  1950s and early 1960s:  Data processing using magnetic tapes for storage  Tapes provide only sequential access  Punched cards for input  Late 1960s and 1970s:  Hard disks allow direct access to data  Network and hierarchical data models in widespread use  Ted Codd defines the relational data model  Would win the ACM Turing Award for this work  IBM Research begins System R prototype  UC Berkeley begins Ingres prototype  High-performance (for the era) transaction processing

History (cont.) 14  1980s:  Research relational prototypes evolve into commercial systems  SQL becomes industry standard  Parallel and distributed database systems  Object-oriented database systems  1990s:  Large decision support and data-mining applications  Large multi-terabyte data warehouses  Emergence of Web commerce  2000s:  XML and XQuery standards  Automated database administration  Increasing use of highly parallel database systems  Web-scale distributed data storage systems

Database models 15 Early Types of DBMS  Hierarchical  Network Current Generation  Relational Advanced Systems - Object Based

What is a Database System? 16 Database System = Database + DBMS  A Database is  A large, integrated collection of data  Models (represents) a real-world enterprise. Entities (e.g., students, courses) Relationships (e.g., Mary takes CS123)  A Database Management System (DBMS) is  A software package designed to store and  Manages databases easily and efficiently.

Common Uses of Databases 17  Try to think why each of these need to use a database:  Supermarkets  Insurance  Credit Cards/Banking  Libraries  Travel Agents  Universities

Examples: DBMS 18  MSAccess  MySQL – freeware (Windows & Unix)  McKoi – freeware, Java based.  Oracle  SQL Server – Microsoft product – we use in this course  Any other ?  Common features:  Relational model  SQL as query language  Server-client architecture

19 Advantages of using a DBMS  Minimal data redundancy  Efficient data access  Data integrity and security  Data administration  Concurrent access, recovery from crashes  Reduced application development time

20 Disadvantages  Complexity  Additional Hardware costs  Experts – Specialised personnel  Higher impact of failure  Simple applications may not need DBMS at all

Questions? 21