DATABASE SYSTEMS VS ROUTINE FILE SYSTEMS
- 1. DATABASE SYSTEMS WEEK 1 LECTURE 1 & 2 AYESHA NASIR
- 2. Course Objectives Introduction to very basics Guides through different design stages Familiarize with tools Emphasis on design stages of database
- 3. Lecture Objectives Some common uses of database systems. Characteristics of file-based systems. Problems with file-based approach. Meaning of the term database. Meaning of the term Database Management System (DBMS). Typical functions of a DBMS. Major components of the DBMS environment. Personnel involved in the DBMS environment.
- 4. Textbook Recommended textbooks: Database Systems: A practical approach to design, implementation and management by Connolly and Begg Fundamentals of Database Systems (7th Edition) by Ramez Elmasri, Shamkant B. Navathe Other textbooks: There are lots of database texts Most of them would be fine also For example: ‘Database Systems’ by CJ Date
- 5. Data vs. Information Data are simply facts or figures — bits of information, but not information itself. When data are processed, interpreted, organized, structured or presented so as to make them meaningful or useful, they are called information. Information provides context for data.
- 6. Graphical displays turn data into useful information that managers can use for decision making and interpretation
- 9. Traditional File Systems File processing systems was an early attempt to computerize the manual filing system that we are all familiar with. A file system is a method for storing and organizing computer files and the data they contain to make it easy to find and access them. File systems may use a storage device such as a hard disk or CD- ROM and involve maintaining the physical location of the files.
- 10. Traditional File Systems The manual filing system works well when the number of items to be stored is small. It even works quite adequately when there are large numbers of items and we have only to store and retrieve them. However, the manual filing system breaks down when we have to cross-reference or process the information in the files.
- 11. Characteristics of File Processing System It is a group of files storing data of an organization. Each file is independent from one another. Each file is called a flat file. Each file contained and processed information for one specific function, such as accounting or inventory. Files are designed by using programs written in programming languages such as C, C++. As systems became more complex, file processing systems offered little flexibility, presented many limitations, and were difficult to maintain.
- 13. Problems With the File System Separated and Isolated Data: To make a decision, a user might need data from two separate files. First, the files were evaluated by analysts and programmers to determine the specific data required from each file and the relationships between the data and then applications could be written in a programming language to process and extract the needed data. Imagine the work involved if data from several files was needed.
- 14. Problems With the File System Duplication of data: Often the same information is stored in more than one file. Uncontrolled duplication of data is not required for several reasons, such as: Duplication is wasteful. It costs time and money to enter the data more than once It takes up additional storage space, again with associated costs.
- 15. Problems With the File System Incompatible file formats: As the structure of files is embedded in the application programs, the structures are dependent on the application programming language. For example, the structure of a file generated by a COBOL program may be different from the structure of a file generated by a 'C' program. The direct incompatibility of such files makes them difficult to process jointly.
- 16. File Based Systems (Summary) File based systems Data is stored in files Each file has a specific format Programs that use these files depend on knowledge about that format Problems: No standards Data duplication Data dependence No way to generate ad hoc queries No provision for security, recovery, concurrency, etc.
- 17. Why Study Databases? Databases are useful Many computing applications deal with large amounts of information Database systems give a set of tools for storing, searching and managing this information
- 18. What is a Database? “A set of information held in a computer” Oxford English Dictionary “One or more large structured sets of persistent data, usually associated with software to update and query the data” Free On-Line Dictionary of Computing “A collection of data arranged for ease and speed of search and retrieval” Dictionary.com
- 19. Databases Library catalogues Medical records Bank accounts Stock control Personnel systems Product catalogues Telephone directories Train timetables Airline bookings Credit card details Student records Customer histories Stock market prices Discussion boards and so on…
- 20. Database Systems A database system consists of Data (the database) Software Hardware Users We focus mainly on the software Database systems allow users to Store Update Retrieve Organise Protect their data.
- 22. Database Users End users Use the database system to achieve some goal Application developers Write software to allow end users to interface with the database system Database Administrator (DBA) Designs & manages the database system Database systems programmer Writes the database software itself
- 23. Database Management Systems A database is a collection of information A database management system (DBMS) is the software which controls that information Examples: Oracle DB2 (IBM) MS SQL Server MS Access Ingres PostgreSQL MySQL
- 24. What the DBMS does Provides users with Data definition language (DDL) Data manipulation language (DML) Data control language (DCL) Often these are all the same language DBMS provides Persistence Concurrency Integrity Security Data independence Data Dictionary Describes the database itself
- 25. Data Dictionary - Metadata The dictionary or catalogue stores information about the database itself This is data about data or ‘metadata’ Almost every aspect of the DBMS uses the dictionary The dictionary holds Descriptions of database objects (tables, users, rules, views, indexes,…) Information about who is using which data (locks) Schemas and mappings
- 26. Relational Systems Information is stored as tuples or records in relations or tables There is a sound mathematical theory of relations Most modern DBMS are based on the relational model The relational model covers 3 areas: Data structure Data integrity Data manipulation More details in the next lecture…
- 27. Next Lecture Database Management System in detail Importance of database design. Database system basic structures.