Week 5 - Databases

Question 1

What is a database

Answer 1

-structured collection of non-redundant data which can be shared by different application systems.

Question 2

models in order of increasing abstraction

Answer 2

• Reality
• Conceptual model
• Logical Model
• Physical Model

Question 3

what is a DBMS

Answer 3

software package that allows for creation, storage, maintenance, manipulation and retrieval of large datasets
-in tabular form

Question 4

Goespatial database management system

Answer 4

• step up from DBMS additionally containing specific geographic information about each data point (line, polygon) such as identity, location, shape and orientation.
• powerful tool to visualise and answer spatially explicit questions.

Question 5

Types of DBMS

Answer 5

• File management system (flat database)
• Hierarchical Database system
• Relational DBMS

Question 6

Flat file Database

Answer 6

-spredsheet

Question 7

Hierarchical Database

Answer 7

• organisational chart in hierarchies
• easy to understand and conceptualise
• efficient and fast access to data via key attributes
• Not ideal for large data sets as it is difficult to modify.

Question 8

Relational database

Answer 8

• collection of tables that are connected by unique identifiers.
• each column represents a particular attribute (e.g area, soil type) FIELDS
• rows–> records
• e.g subject info and student info tables both have school column

Question 9

Primary key

Answer 9

attributes of a table (column) used to uniquely identify each of the rows in a table.
- can’t be an attribute that produces duplicate values in the rows.

Question 10

Foreign key

Answer 10

primary key that corresponds to an identical attribute in a secondary table.
-means of interconnecting data stored in different tables.

Question 11

SQL

Answer 11

natural query language

Question 12

Relational DBMS criteria

Answer 12

• flexible in design and queries
• simple and intuitive
• minimize duplication
• uses SQL

Question 13

a query selects rows in a table if ..

Answer 13

a condition is true

Question 14

Boolean operators

Answer 14

combine conditions with logical expressions: AND, OR, NOT. Conjunctions to combine or exclude keywords in a search.
-given results are true or false

Question 15

features in a Geodatabase are stored in which format?

Answer 15

relational database

Question 16

what does a geodatabase contain?

Answer 16

• Table (rows all contain the same fields)
• Feature class (tables with shape fields (point, line polygon)
• raster dataset
• USI for each feature

Question 17

Joins

Answer 17

linking separate tables in relational DBMS

• Joins: appends fields from one table to another based on a common attribute. Non-spatial data tables
• Spatial join: combines feature information based on spatial location.

Question 18

Joins vs. relates

Answer 18

• joins for suitable for 1-1 or many-1 relationships
• joins present data from two two tables in readily available single output table.
• relates are suitable for all relationships (1-many, many-many)
• relate produced very large table.

Question 19

2 spatial query methods

Answer 19

1. Coordinate: distance from a feature

2. topologyical relation (contained in, overlap, intersect)

Question 20

Join e.g

Answer 20

PARCEL table: multiple Parcel attributes (LotPlan ID, Code, Adress)

combined with

PARCEL OWNER table outlining parcel owner (1 attribute).

Many-1

Question 21

Centralised database

Answer 21

-physically confined to one location under the control of a single computer

Question 22

Distributed databse system

Answer 22

several systems at local sites connected by communication lines
-multiple databses

Question 23

Stage of increasing abstraction (which database model)

Answer 23

• Proceeds conceptual model to a logical database model