1. Database Management System Lecture 2 Introduction to Database management

2. Learning Outcomes Understanding the definition of a Database management System (DBMS) Grasping an outline of DBMS architectures Understanding DBMS’s main functionalities Get introduced to a number of commercial DBMSs which are widely used.

3. List of Topic DBMS definition DBMS functionalities DBMS Examples

4. Terminology 1DatabaseA collection of related information stored in a structured format 2DBMSDatabase management system. A program or environment which hosts one database or more and provide support for managing information in such databases 3TableA single store of related information. A table consists of records, and each record is made up of a number of fields

5. Terminology 4SQLIt stands for Structured Query Language, the standard format for commands that most database software understands 5RDBMSRelational DBMS

6. DBMS definition DBMS is a collection of software for creating, managing and effectively searching a database. DBMS Role Illustration

7. DBMS definition (con.) In addition a DBMS is responsible for managing application requests to a database

8. DBMS Three-Schema Architecture

9. DBMS Three-Schema Architecture (con.) The architecture ensures: the independence of logical and physical data allowing the manipulation of data ensure data integrity optimize data access.

10. DBMS Three-Schema Architecture (con.) 1- External layer or External Schema It covers all the possibilities of access to data by different users. Access of different user groups can be done via different applications.

11. DBMS Three-Schema Architecture (con.) 2- Each external schema describes the part of the database that a particular user is interested in hides the rest of the database from user.

12. DBMS Three-Schema Architecture (con.) 2-Logical Layer or Logical Schema It is the general view of the data independent of individual applications and how data is stored. It hides the details of physical storage structures and concentrates on describing entities, data types, relationships, user operations, and constraints.

13. DBMS Three-Schema Architecture (con.) 3- Internal layer or Internal Schema Describes the physical storage structure of the database. The internal schema describes the complete details of data storage and access paths for the database.

14. DBMS Functionalities 1-Support the concepts defined in the data model in order to represent data properties. It usually includes the definition of specific types and the definition of consistency rules.

15. DBMS Functionalities (con.) 2-Make transparent data sharing between different users. This means that multiple users should be able to use the database concurrently and transparently

16. DBMS Functionalities (con.) 3-Ensure confidentiality of data to specify who has the right to access or modify all or part of a database. first requires a user identification second requires a specification of privileges (add, delete, update).

17. DBMS Functionalities (con.) 4-Ensure compliance with the consistency rules defined on the data after each modification on the database, all rules of consistency must be checked on all data

18. DBMS Functionalities (con.) 5-Being resistant to failure. this is to protect data against hardware failure or software whether intentional or accidental.

19. DBMS Functionalities (con.) 6- Possess a high storage capacity Thus enabling data management up to several billion bytes The storage units are moved from the megabyte (10 6 ) to gigabyte (10 9 ), then to terabyte (10 12 ), peta-byte (10 16 ), and we start talking about exabytes (10 18 ) even zettabyte (10 21 ).

20. DBMS Functionalities (con.) 7- To answer queries with a level of acceptable performance A query requires searching data in a database based on some conditions Computer power is not the only possible answer to the problems of performance Query optimization can be very effective to ensure

21. Database Examples Is widely used due to its ease of integration with the Apache/PHP and its good response time. MySQL supports only part of the standard SQL-92.

22. Database Examples (con.) 1.MySQL: It does not support native transactions, subqueries, triggers and stored procedures. Lacks some features compared to other DBMSs

23. Database Examples (con.) 2Oracle is a RDBMS which supports remote access to the database hosted in it. It is one of the best performing DBMS with powerful tools. Oracle is a RDBMS-oriented environments with heavy constraints (availability, integrity, stability, large volumes of data and high number of users, etc..).

24. Database Examples (con.) 3PostgreSQL PostgreSQL is usable under Linux. Is an excellent choice to manage databases of medium size. It is free.

25. Database Examples (con.) 4Borland Interbase One of its main strengths is its availability in an open source version A good choice to manage databases for small and medium size

26. Database Examples (con.) 5Microsoft SQL Server SQL Server is a good choice for databases of medium size

27. Database Examples (con.) 6Access Developed by Microsoft Suitable for supporting small databases (personal ).

28. Summary In this lesson, the following has been discussed: The definition of DBMS and its role. The DBMS architecture based on the three-schema architecture. The main features that a robust and reliable DBMS must have. An outline of the most widely used DBMSs.

29. Exercises What are the three layers constituting a DBMS architecture ? Which layer in DBMS architecture interacts with end users or user applications ? List the most important features which must belong to a DBMS? List four widely used DBMSs?

30. Self-assessment 1Search the web and find a good reference for the SQL language. Identify the SQL command that could be used to: Create a table. Insert a record in a table. Modify a data field in a table record.