January/February Flashcards
(46 cards)
Databases typically contain many ______.
files
Why bother with a 90-file .gdb over a 24-file .shp format?
- Concurrency
- Integrity
- Dependence
- Different Views
Concurrency
Access by multiple people
Integrity
Data meets specified criteria
Dependence
Relationships between data values
Different views
Meet different user eneds (general manager vs forest manager example)
DBMS
Database Management System
User–>Query OR Update–>Compiler–>Constraint enforcer–>Database processor–>Data manager–>Sends query results back to user
A database transaction is a single (_____) interaction between….
“atomic”…..the user and the database
What are types of transactions in a database?
Adding or editing (new data), deleting data, and retrieving data
DBMS’s have __________ or “interleaved”
many transactions happening simultaneously
Database Schema
Structured representation of a table
-What is its name?
-What are its attributes?
-For each attribute, what is the domain of said attribute? (e.g. integers, Boolean, text, anything 0-14)
Files/data/tables need a way to ______, which is where ______ come in handy.
talk to each other, relational databases/entity-relationship models
Database Development Chart
Domain Model –> Concept Computation Model –> Logical Computation Model –> Physical Computation Model
The entity-relationship model is based on…..
relational database framework
Give an example of entity types/instances/attributes
In a table of cities, cities is the entity type, rows are entity instances, and columns are attributes
Primary key
A unique identifier (e.g. FIPS and FID)
Primary keys are often….
a number, not a name
The relationship aspect of a ER model is….
what links the entities to one another
We often use a ____ shape to conceptualize relationships
diamond
Numbers next to entities signify….
how many of one entity can be matched to the other entity
What are the types of matches between entities?
- 1 to 1
- 1 to many (1 city and many wards in that city)
- many to 1 (many cities in 1 county)
- many to many (many rivers in each city, and many cities along each river)
What number is used to express many match possibilities?
[0…n]
Explain the concept of mandatory vs. optional relationships
Using the city-contains-county model:
- Each city MUST be contained within exactly 1 county, as represented by double lines
- A county doesn’t have to contain any cities, as represented by a single line
Explain the concept of involutary relationships
Using the city-county-borders example:
- The M&N denote a many-to-many relationship, and the chart serves to express what counties border each other (?)
