Databases-Introduction to Database System-Lecture 01 Slides-Computer Science, Slides of Introduction to Database Management Systems

Download Databases-Introduction to Database System-Lecture 01 Slides-Computer Science and more Slides Introduction to Database Management Systems in PDF only on Docsity! 1 Introduction to Database Systems G52DBS – Database Systems www.cs.nott.ac.uk/~smx/DBS 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 • Databases in CS • Databases are a ‘core topic’ in computer science • Basic concepts and skills with database systems are part of the skill set you will be assumed to have as a CS graduate Introduction to Database Systems G52DBS – Database Systems www.cs.nott.ac.uk/~smx/DBS 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 Introduction to Database Systems G52DBS – Database Systems www.cs.nott.ac.uk/~smx/DBS Databases • Web indexes • 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… Introduction to Database Systems G52DBS – Database Systems www.cs.nott.ac.uk/~smx/DBS 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. Introduction to Database Systems G52DBS – Database Systems www.cs.nott.ac.uk/~smx/DBS 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 Introduction to Database Systems G52DBS – Database Systems www.cs.nott.ac.uk/~smx/DBS Database Management Systems • A database is a collection of information • A database management system (DBMS) is the software than controls that information • Examples: • Oracle • DB2 (IBM) • MS SQL Server • MS Access • Ingres • PostgreSQL • MySQL 2 Introduction to Database Systems G52DBS – Database Systems www.cs.nott.ac.uk/~smx/DBS 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 Introduction to Database Systems G52DBS – Database Systems www.cs.nott.ac.uk/~smx/DBS Data Dictionary - Metadata • The dictionary or catalog 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 • The dictionary itself Introduction to Database Systems G52DBS – Database Systems www.cs.nott.ac.uk/~smx/DBS File Based Systems • 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. Introduction to Database Systems G52DBS – Database Systems www.cs.nott.ac.uk/~smx/DBS Relational Systems • Problems with early databases • Navigating the records requires complex programs • There is minimal data independence • No theoretical foundations • Then, in 1970, E. F. Codd wrote “A Relational Model of Data for Large Shared Databanks” and introduced the relational model Introduction to Database Systems G52DBS – Database Systems www.cs.nott.ac.uk/~smx/DBS 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 detail next lecture… Introduction to Database Systems G52DBS – Database Systems www.cs.nott.ac.uk/~smx/DBS ANSI/SPARC Architecture • ANSI - American National Standards Institute • SPARC - Standards Planning and Requirements Committee • 1975 - proposed a framework for DBs • A three-level architecture • Internal level: For systems designers • Conceptual level: For database designers and administrators • External level: For database users