Transcript Chapter 1 Computer Basics

Chapter 9
Databases
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.
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.
DBMS components
Database architecture
DB models - hierarchical
DB models – network
DB model - relational
Relation
• A relation, in appearance, is a twodementional table.
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-bystep procedure.
Operations on relations - insert
insert into COURSES
values (“CIS52”, “TCP/IP Protocols”, 6)
Operations on relations - delete
delete from COURSES
where No=“CIS19”
Operations on relations - update
update COURSES
set Unit = 6
where No = “CIS51”
Operations on relations - select
select *
from COURSES
where Unit = 5
Operations on relations - project
select No, Unit
from COURSES
Operations on relations - join
select No, Course-Name, Unit, Professor
from COURSES, TAUGHT-BY
where COURSES.No = TAUGHT-BY.No
Operations on relations - union
select *
from CIS15-Roster
union
select *
from CIS52-Roster
Operations on relations intersection
select * from CIS15-Roster
intersection
select * from CIS52-Roster
Operations on relations difference
select * from CIS15-Roster
minus
select * from CIS52-Roster
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.