introduction Flashcards
what is data
anything that can be represented in binary
what is data engineering
designing and building systems so data can ve collected managed and analysed
what is a database
structured systems for storing retrieving and managing data
what is raw data
data kept in an excel file
data model
defines how data will be related and stored
what are some negatives of file processing applications
would have to hire a developer as they were hard to implement which is expensive
issues with optimisation performance reliability and reuse
what is a file processing application
a set of files that are processed to retrieve information
logical model
allows a logical representation which aids processing which can be represented graphically via an entity relationship diagram
dbms
database management system; uses the logical model to control the database and provides efficient reliable multi-user storage and access to large amounts of persistent data
what is the difference between source code, a program, and software
source code; code written by developers that isn’t directly executable
program; what you get when the source code is executed
software; the entire collection of programs, libraries and related data
ddl (data definition language)
creates tables
dml (data manipulation language)
modifies tables
what is an entity and how is it represented in an er diagram
an object with distinguishable attributes
rectangle
entity set
a representation of entities with the same set of attributes
what is an attribute and how is it represented in an er diagram
information that describes an aspect of an entity
oval
primary key
unique identifier for an entitiy
what is a derived attribute and how is it represented in an er diagram
an imaginary attribute not stored in the database but derived using system recourses
dashed/broken oval
what are multi-valued attributes and how are they represented in an er model
attributes with more than one value
double oval
composite attributes
an imaginary group of attributes not in the table that groups together existing attributes
relation
a logical model for associating 2 or more entities
what is a relationship set and how is it represented in an er model
a set of all relationship that can have attributes and a primary key
diamond
degree of relationship set
number of different entity sets in the relationship
one to one relationship
created whilst creating the table and can lead to new tables
total participation (must)
for every entity in an entity set, it must relate to at least another entity in the other set
partial participation (may)
not all entities have to map to another entity in the other set
what is combined to create the subject table key
owner table primary key + subject table weak key
overlap constraints
restrictions on the relationship between different entities, ensuring that they don’t simultaneously occupy conflicting roles
covering constraints
ensures that everything is correctly classified within the appropriate categories and leaving no gaps in the er model
what are the 2 reasons that we use ISA
identifies entities that participate in relationships
adds descriptive attributes to a specific subclass
