90 likes | 273 Vues
DATABASE MANAGEMENT. BY GOBETTI ANDREA. What is a database?. Integrated set of data files allows easy cross-referencing of related data items promotes integrity eliminates redundancy. Differences between database and file management software. Allow to manipulate data Create reports
E N D
DATABASE MANAGEMENT BY GOBETTI ANDREA
What is a database? • Integrated set of data files • allows easy cross-referencing of related data items • promotes integrity • eliminates redundancy
Differencesbetween database and file management software • Allow to manipulate data • Create reports • Handle individual enquires • F.M.S. works with only one file at time
Database models • Hierarchical • Network • Relational
Hierarchical model • Data items and references are related in a top-down structure • Makes possible orderly navigation of paths to the desired information • The same path must be followed for each access operation
Network model • There’s always a hierarchical structure • “Random Access” is possible • Multiple access paths are possible between records
Relational model • A series of files organized as data tables • Some relation tables to link data together • “Random Access” is possible
DBMS (DataBase Management System) Some essencial facilities: • Create (table with fields) • Insert (records into tables) • Amend and delete • Search