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What is a Database System?

What is a Database System?. Lecture 1. Informal introduction. what do you think a database system is? think of some (real life) examples of database systems main features provided by a database system store (insert, delete and update) and retrieve data.

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What is a Database System?

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  1. What is a Database System? Lecture 1

  2. Informal introduction • what do you think a database system is? • think of some (real life) examples of database systems • main features provided by a database system • store (insert, delete and update) and retrieve data

  3. Example: part of a relational database

  4. Database / file-based system • definition • … is a software (computer program, system) that provides assistance in the management of data • approaches • decentralised  file based system • centralised  database system

  5. Property for rent file PropertyId Street Area City PostCode Type NoOfRooms RentOwnerId Owner file OwnerId FirstName LastName Address TelNo Renter file RenterId FirstName LastName Address TelNo PreferredType MaxRent File-based system : Sales Dept’s files Sales Department files

  6. Owner file OwnerId FirstName LastName Address TelNo Property for rent file PropertyId Street Area City PostCode Rent Renter file RenterId FirstName LastName Address TelNo Lease file LeaseID PropertyId RenterId OwnerId Rent TypeOfPayment Deposit Start Finish File-based system : Contracts Dept’s files Contracts Department files

  7. Files of Application 1 Application 1 group 1 of users Files of Application 2 Application 2 group 2 of users Files of Application n Application n group n of users The file-based approach

  8. File based systems - limitations • duplication of data • wasteful • prone to inconsistencies • separation and isolation of data • data cannot be used together • incompatible file formats • program-data dependence • incompatible file formats • fixed queries

  9. Database / database system • definition • a database (DB) is a shared collection of logically related persistent data as part of the information system of an organisation • main points • persistent data • logically related data • shared • database system • database + the operations defined on it

  10. DBMS Application 1 group 1 of users DB raw data + data dict. DB Application 2 group 2 of users Application n group n of users The database approach

  11. Database management system • definition • a database management system (DBMS) is a software that provides a set of primitives for defining, accessing and manipulating data

  12. Summary • real life examples of database systems • file-based systems • database systems • database (DB) • database system • database management system (DBMS)

  13. Activity A1 Think of a real life system for data management developed in a file-based approach (i.e. a system that you have or might have come across). What disadvantages do you identify? Could any of them be solved by adopting a database approach? Does the database approach solution introduce any disadvantages?

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