Topic 06

Question 1

4 cardinalities of database

Answer 1

one to one

one to many

many to many

many to one

Question 2

what is spatial data “special”

Answer 2

the geographic world doesnt fit well into the flat tables so GIS databases are often much more complex then non-spatial databases

Question 3

database

Answer 3

facilitates efficient storage and retrival of data

capable of manipulating large columves of data

tools for managing, protecting, controlling, maintaining spatial integrity

steps beyond excel functions

Question 4

advanced features of a database

Answer 4

data security

maintain integrity

allow concurrent access

support user queries while managing security

independence of data/human database interaction

automatic of tasks

Question 5

easiest way to store data

Answer 5

the simplest forms is in a flat table

consists of records (rows) and attributes (columns)

Question 6

problems iwth single tables

Answer 6

easy to use for limited amounts of data

not efficient for large or complex data

redundant data causes issues

Question 7

limitations of single flat tables

Answer 7

produces redundant data

inefficient data entry, storage and queries

Question 8

limitations continued (typographical errors)

Answer 8

lots of errors in existing data
these errors are not understood by the computer

ex. using Mr. Mr, Sir for the same person is seen as different by the computer

Question 9

updating data in a single table

Answer 9

can be problematic to existing data entries

Question 10

modifying data in a single table

Answer 10

problems with how data is set up and new entries

best solves
store data in a different table

Question 11

use of multiple tables

Answer 11

reduces or solves the main problems with single tables

original info can be reproduced from the information in the new tables

Question 12

making tables work together

Answer 12

essentially relational databases do two things that allow us to store information about the real world

Question 13

creating ‘correct’ tables

Answer 13

rule of thumb: provide a separate table for each real world entity for you are storing informaton

ex a customer, employee, an order, a product

data normalization: ensure appropriate defined tables

Question 14

relating tables

Answer 14

should follow the logical relationships between the real world entities

Question 15

one to one relationship

Answer 15

one entity (record)in a table is associated with one and only one entity (record) in a related table

ex. employee and IT email

Question 16

one to many relationship

Answer 16

one entity in a table associated with many entities in another table

ex. customer to several orders

Question 17

many to many relationship

Answer 17

many records associated with multiple records in another table

ex. multiple customers linked to multiple employees

Question 18

modelling relationships

Answer 18

The conceptual model defines how the user views the database

Question 19

levels of data model abstraction

Answer 19

increasing abstraction

1. reality
2. conceptual model
3. logical model
4. physical model

Question 20

keys and joins

Answer 20

used to implement relationships among entities in a database

always used together

Question 21

keys

Answer 21

a filed (column) in a table used to identify a record

Question 22

primary key

Answer 22

unique

provides information to uniquely identify a record

ex. employee ID number

Question 23

foreign key

Answer 23

in another table

join one table to another

creates a logical data model that defines the structure of the database

how many things are being connected*

Question 24

data integrity

Answer 24

preserves the accuracy of the information

keeps all the data reliable

not all errors can be avoided

lots can be identified by enforcing data integrity rules

Question 25

four types of integrity errors

Answer 25

errors in standardized data erros in non standardized data error between data in different fields errors between keys in different tables

Question 26

validation rules

Answer 26

enforcing appropriate data types

Question 27

errors in non standardized data

Answer 27

entry errors are very critical errors may occur in standardized data that exist in a single field often errors like this can be detected if one uses validation rules

Question 28

ways to check and fix validation rules

Answer 28

enforcing appropriate data types attribute domains validation functions uniqueness

Question 29

validation rules: attribute domains

Answer 29

the most common type uses limits or constrains the type of information that can entered ex. number only for birth year

Question 30

validation rules: validation functions

Answer 30

custom designed expressions, scrpts, code powerful method

Question 31

validation rules: uniqueness

Answer 31

a built in validation rule that is often used with keys to check for unique values

Question 32

errors in non-standardized data

Answer 32

logical consistency can be checked for errors

Question 33

errors between keys in different tables

Answer 33

referred to as errors of referntia integrity occurs when there Is an incosistency between tables

Question 34

referential integrity

Answer 34

powerful tools to chec and maintain referential integrity among tables that exist in most databases the most common checks between tables 1. deletions in one table can be checked to all related tables 2. updates information in one table can be checked to related tables

Question 35

indexes

Answer 35

are another powerful feature of databases that separate them from other methods to store data such as spreadsheets used to speed up searches and queries for your database

Question 36

why to use indexes

Answer 36

easy to find info when organized efficiently cross referenced with other things ex. name in phonebook

Question 37

how do indexes work

Answer 37

essentially a join can have multiple indexes sortsbased on order

Question 38

pros of indexes

Answer 38

improves searching speed

Question 39

cons of indexes

Answer 39

slows data entry and updates increases size of database and redundencies

Question 40

when to use indexes

Answer 40

used as a key or field used to query the data

Question 41

when not to use indexes

Answer 41

onevery field in the table fields that wont be searched constant inputs or updates to the entries