1. What is a Database System? 1 Lecture 1

2. What is a Database System? 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. What is a Database System? 3 Example: part of a relational database

4. What is a Database System? 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. What is a Database System? 5 File-based system : Sales Depts files Sales Department files PropertyId Street Area City PostCode Type NoOfRooms Rent OwnerId Property for rent file OwnerId FirstName LastName Address TelNo Owner file RenterId FirstName LastName Address TelNo PreferredType MaxRent Renter file

6. What is a Database System? 6 File-based system : Contracts Depts files Contracts Department files PropertyId Street Area City PostCode Rent Property for rent file RenterId FirstName LastName Address TelNo Renter file LeaseID PropertyId RenterId OwnerId Rent TypeOfPayment Deposit Start Finish Lease file OwnerId FirstName LastName Address TelNo Owner file

7. What is a Database System? 7 The file-based approach group n of users group 2 of users group 1 of users Application 1 Files of Application 1 Application 2 Application n Files of Application 2 Files of Application n

8. What is a Database System? 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. What is a Database System? 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. What is a Database System? 10 The database approach group n of users group 2 of users group 1 of users Application 1 Application 2 Application n DB DBMS DB raw data + data dict.

11. What is a Database System? 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. What is a Database System? 12 Summary real life examples of database systems file-based systems database systems database (DB) database system database management system (DBMS)

13. What is a Database System? 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?