session 7: fundamentals of relational database operations Flashcards
data file
collection of logically related records
data hierarchy
bit
byte
field
record
data file/table
database
bit def
smallest unit of data, 0 to 1
byte def
group of 8 byte, single character
field def
logical grouping of characters into a word, a small group of words, identification #
record def
logical grouping of related fields such as student’s name, the course taken and the grade
data file/table
logical grouping of records
relational database
collection of interrelated two-dimensional tables consisting of rows and columns
DBMS data base management system
set of programs with tools to create and manage databases. Meaning adding, deleting, accessing, modifying, and analyzing data that are stored in the database.
Can access the data with query and reporting tools or apps.
DBMS minimizes
data redundancy
data isolation: application cannot access data associated with other apps
data inconsistency
DMBS maximizes
Data security: data is put in one place, risk of losing it all at once
Data integrity: meets certain constraints
Dara independence: applications and data independent so all apps are able to access same data
data model def
a diagram that represents entities in the database and their relationships
entity def
a person, place, thing about whihc an organization maintain info about
instance def
each row in a relational table which is a specific unique representation of the entity
ex: entity is student and instance of the entity would be a particular student
attribute def
each characteristic or quality particular to an entity
ex: if entity is customers attribute would be name , employee number and product colour
primary key def
the identifier field or attribute
foreign key def
a field or group of field in 1 unique table that uniquely identifies a row of another table
secondary key def
a field that has some identifying info but typically does not identify the record with complete accuracy
query language
Structured Query Language (SQL)
Query by Exqmple (QBE)
SQL
allows people to do complicated searches by using relatively simple statements/key words (SELECT, FROM, WHERE)
QBE
the users fill out a grid or template (“form”) to construct a sample or description of data desired
relationships illustrate…
….an association between entities
degree of relationships
number of entities associated with a relationship
entity-relationship diagram (ERD)
doc that shows data entities + attributes + relationships among them
business rules def
precision description of policies/procedures/principles in any organization
data dictionary def
provides info on each attribute such as its name
relationships type
unary
binary
ternary
unary relationship def
a relationship that exists when an association is maintained within a single entity
binary relationship def
a relationships that exists when 2 entities are associated
ternary relationship def
a relationship that exists when 3 entities are associated
cardinality def
max number of times an instance of an entity can be associated with an instance in the related entity
connectivity def
describes the relationship classification
normalization def
method for analyzing/reducing a relational database to its most streamlined form
limit redundancy, maximum integrity and optimal processing performance
1st normal form to 3rd
functiunal dependencies def
a means of expressing that the value of one particular attrbute is associated with or determines a specific single value of another attribute
join operation def
a database operation that combines records from 2 or more tables in a database
relational database model def
usually designed with a number of related tables each of which contains records (listed in rows) and attributes (listed in columns)
advantage and disadvantages of relational databases
enable people to compare info quickly by row or column
users can easily retrieve items by finding the point of intersection of a particular row and column
large scale relational database can be composed of numerous interrelated tables => design more complex => slow search and access time
entity relationship modelling def
the process of designing a database by organizing data entities to be used and identifying the relationships among them
third normal form characteristics
free of data redudancy
all foreign keys appear where needed to link related tables
