Chapter 2, Understanding Data

Question 1

Which common encoding standard (character set) enables use of non-Latin characters?

Answer 1

UTF-8

Question 2

Which data type is used to store status of a flag?

Answer 2

The Bit data type

Question 3

The author states there are two data-types relating to numbers. what are these and what’s the different between them and what does the author get wrong?

Answer 3

Integer - used for whole numbers only
Numeric - used for numbers with a decimal point (rational numbers)
The author uses numeric to describe numbers with a decimal point when this is ambiguous. It should be Floating Point/Decimal and not ‘Numeric’

Question 4

Name the 3 types of rational number datatypes named in the book?
Which ones aren’t used by Microsoft SQL server and MySQL?

Answer 4

Decimal, Shortdecimal and number
shortdecimal and number is not used by Microsoft SQL server or MySQL

Question 5

Which database discussed in the book is the only one that had datatypes specifically for storing currency?

Answer 5

Microsoft SQL

Question 6

For what reason does the currency datatype not really get used?

Answer 6

The currency data type uses floating-point numbers as it’s underlying data-type. As they’re stored as binary numbers, they suffer from binary rounding errors.

The book mentions the reason is due to the 4 decimal place limitation, this is nonsense. It could be 10 decimal places, and there would still be rounding errors because Currency is floating-point and stored as binary. However, 4 is still limited as there are many examples in financial calculations where you need more than this.

Question 7

Which data type would you pick if you had to store unstructured data in the form of Office files?

Answer 7

binary datatype

Question 8

Aside from being character/alphanumeric data types, what data structure would large text datatype names longtext,varchar(max) and CLOB fall into?

Answer 8

Unstructured - because all of these data-types could hold many paragraphs worth of unstructured text

Question 9

A ____ _______ is an attribute about a person, place or thing.

Answer 9

data element

Question 10

What describes the characteristics of activities?

Answer 10

Data elements

Review book. This question needs more context.

Question 11

What kind of data is organized into a table made up of rows and columns?

Answer 11

Tabular data

Question 12

What kind of database is an extension of the tabular model and organizes data across multiple tables instead of having it all in just one table?

Answer 12

An RDMS or Relational Database Management System

Question 13

What makes structured data structured?

Answer 13

1) it is tabular in nature
2) the columns have consistent data types, i.e. Only seeing numbers in the “Weight” column.

Question 14

What is the most common data-type used to store Characters in a cell?

Answer 14

Alphanumeric

Question 15

Describe strong typing and weak typing?

Answer 15

Strong typing refers to the strictly enforced type of data that is allowed in a database cell. The cell simply won’t accept a data type outside of what is configured. Whereas weak typing refers to what is used in spreadsheets in which they loosely enforce a data type allowed in a given cell. The software will still allow a different data type to be used.

Question 16

Regardless of structure, data is either __________ or ___________

Answer 16

Qualitative, Quantitative

Question 17

General numeric data comes in two forms. What are they called, what data-types are associated with each and what are each used for typically?

Answer 17

1) Discrete numbers. Use the Integer datatype. Used when counting something.
and
2) Continuous - use Decimal/Floatin point usually. Used when measuring.

Discrete numbers are always integers and can’t be subdivided into fractions.

Question 18

two examples of data below. Which is discrete and which is continuous? Why?

Number of Dogs - 5
Average Miles walked - 505.5

Answer 18

Number of dogs is discrete because you can’t subdivide one dog.
Average miles walked is continuous because you can subdivide a mile.

Question 19

Why can qualitative data only be discrete but quantitative data can be both discrete and continuous?

Answer 19

qualitative data can only be discrete because qualities like hair colour, name, sex etc can’t be subdivided whereas quantitative data can be both discrete if specified or continuous if measuring.

Question 20

What are fact tables and what are they used for?

Answer 20

Fact tables can be any table that stores measurable facts or data specific to a business area or process. They’re used with dimension tables to help businesses answer questions

Question 21

What are dimension tables and what are they used for?

Answer 21

Dimension tables are used in conjunction with Fact tables. They simply help answer questions about ‘fact table’, businesses ask questions about things to do with the fact table.

Question 22

What kind of data describes a data element that divides data into distinct groups?

Answer 22

Categorical data.

Question 23

When is data in a column said to be CONSISTENT?

Answer 23

When the data is all of the same type of value

Question 24

Data that has structure but is not tabular is what kind of data?

Answer 24

semi-structured data

Question 25

When dealing with data, what influences your choice of data and why is your choice of data important?

Answer 25

The data values influence your choice of data.
You choice of data is important because it helps boost data quality.

Question 26

The first step in preparing your STRUCTURED data for analysis is doing what?

Answer 26

Getting it into tabular format of unique rows and columns.

Question 27

What are the exam essentials to remember from Chapter 2?

Answer 27

1) Consider the values of what you will store before selecting data types
2) Know that you can format data after storing it
3) Consider the ABSOLUTE LIMITS of values that you will use before selecting data types
4) Explain the differences between structured and unstructured data

Check the book about the values bit.

Question 28

using categories or categorical data has the added benefit of what?

Answer 28

enforcing data quality by restricting input to a finite selection

Question 29

What two things should you consider BEFORE selecting the data-type?

Answer 29

1) what the nature of the data is (text, number binary etc)
2) the size of the data and expected range

Question 30

Machine data is a common source of structured/unstructured data?

Answer 30

Unstructured

Question 31

what type of data storasge architecture is used to store unstructured data?

Answer 31

Object Storage

Question 32

Waht are the largest character data-types in the below databases?
1) Oracle
2) Microsoft SQL Server
3) MySQL

Answer 32

1) Oracle - CLOB 128TB
2) Microsoft SQL Server varchar(max) 2GB
3) MySQL - LONGTEXT 4Gb

Question 33

Which Integer data-types store numbers upto 2.14 trillion?

Answer 33

int, and integer

Question 34

What are the names of the Integer data-types used to store numbers larger than 2.14 trillion?

Answer 34

longinteger and bigint

Question 35

smallint and shortinteger store numbers upto how many?

Answer 35

32,768?

Question 36

the data-type name of Timestamp stores what data in Oracle?

Answer 36

Date and Time

Question 37

if you want to store just the time in a column, which of the databases below supports that?
1) Oracle
2) Microsoft SQL Server
3) MySQL

Answer 37

2) Microsoft SQL Server
3) MySQL

Question 38

List, in order from largest to smallest, the top 3 binary datatypes and their databases

Answer 38

1) BLOB - 128TB - Oracle
2) longblob - 4GB - My SQL
3) varbinary(max) - 2GB - Microsoft SQL Server

Question 39

What activity involves ensuring consistent naming conventions for individual fields are applied? What issue can this cause with visualization and reporting?

Answer 39

Field Standardization

it can cause odd results

Question 40

another name for field

Answer 40

observation