What is a database? Example of database application: –Banks, –Hospital, –etc Extensions: –Multimedia databases –Geographic Information Systems –Data warehouse –On-line analytical processing (OLAP) –Active & real-time databases –etc

What is a database? Basic definition: Database: A collection of related data. Data: Known facts that can be recorded and have an implicit meaning. Mini-world: Some part of the real world about which data is stored in a database. For example, student grades and transcripts at a university.

More about database definition What is a database? Quite simply, it’s an organized collection of data. A database management system (DBMS) such as Access, FileMaker, Lotus Notes, Oracle or SQL Server which provides you with the software tools you need to organize that data in a flexible manner. It includes tools to add, modify or delete data from the database, ask questions (or queries) about the data stored in the database and produce reports summarizing selected contents.

Data vs. information: What is the difference? What is data? –Data can be defined in many ways. Information science defines data as unprocessed information. What is information? –Information is data that have been organized and communicated in a coherent and meaningful manner. –Data is converted into information, and information is converted into knowledge. –Knowledge; information evaluated and organized so that it can be used purposefully.

Andi Name 19 AgeSexID Ina002P L UdinL 20 Character Field Record Database File/Table Student File Item Data Record Data Squence

Problems with file systems Data are Still Highly Redundant – Sharing Limited and at the File Level Data is Unstructured – “Flat” Files High Maintenance Costs – Data Dependence – Ensuring Data Consistency and Controlling Access to Data (Concurrent Access Problematic) – Difficult to Understand by New Developers Difficulties in Developing New Applications Almost Impossible to Evolve with New Capabilities Risk of Inefficient Applications

Database vs. File Systems Coordinates Both Physical and Logical Access to the Data Data are Shared by All Programs Authorized to Have Access to It Flexible Access to Data (i.e., Queries) Multiple Users Accessing the Same Data at Same Time Coordinates Only the Physical Access to the Data Data Written by One Program May Not Be Readable by Another Program Pre-determined Access to Data (I.E., Compiled Programs) No Two Programs Can Concurrently Access the Same File