2. Chapter 9 Databases

3. Objectives Understand a DBMS and define its components. Understand the architecture of a DBMS and its levels. Distinguish between different database models. Understand the concept of relational database operations on a relation. Use Structured Query Language (SQL) to define simple relations.

4. Databases and DBMS A database is a collection of data that is logically, but not necessarily physically, coherent. A database management system defines, creates, and maintains a database. It also allows users controlled access to data in the database.

5. DBMS components

6. Database architecture

7. DB models - hierarchical

8. DB models – network

9. DB model - relational

10. Relation A relation, in appearance, is a two- dementional table.

11. SQL The structured query language is the standardized language we use to operate on relational databases. It is a declarative (not procedural) language, which means that the users declare what they want without having to write a step-by- step procedure.

12. Operations on relations - insert insert into COURSES values (“CIS52”, “TCP/IP Protocols”, 6)

13. Operations on relations - delete delete from COURSES where No=“CIS19”

14. Operations on relations - update update COURSES set Unit = 6 where No = “CIS51”

15. Operations on relations - select select * from COURSES where Unit = 5

16. Operations on relations - project select No, Unit from COURSES

17. Operations on relations - join select No, Course-Name, Unit, Professor from COURSES, TAUGHT-BY where COURSES.No = TAUGHT-BY.No

18. Operations on relations - union select * from CIS15-Roster union select * from CIS52-Roster

19. Operations on relations - intersection select * from CIS15-Roster intersection select * from CIS52-Roster

20. Operations on relations - difference select * from CIS15-Roster minus select * from CIS52-Roster

21. Objectives Understand a DBMS and define its components. Understand the architecture of a DBMS and its levels. Distinguish between different database models. Understand the concept of relational database operations on a relation. Use Structured Query Language (SQL) to define simple relations.