data final

Relational database

tables that connect to each other

Purpose of a database

store and organize data

What can be stored

numbers words dates images

Data model

picture of how data is organized

Table

a place to store related data

Record

one row of data

Field

one column of data

Primary key

unique id for each row

Foreign key

links one table to another

Parent table

has the main id

Child table

uses the id from parent

Referential integrity

data must match between tables

Database vs spreadsheet

database is better for big complex data

Transactional data

day to day data

Analytical data

used to make decisions

Data quality

how good the data is

High quality data

accurate complete consistent

Low quality data

messy wrong missing

Why clean data

to fix errors

Remove duplicates

delete repeats

Trim

remove extra spaces

Split column

break data into parts

Concatenate

combine data

Replace values

fix wrong data

Query

ask for data

Aggregation

summarize data

Sum

add numbers

Average

find mean

Count

count all

Count distinct

count unique

Group by

put data into groups

Sort

order data

Filter

show only some data

AND

all conditions must be true

OR

only one condition must be true

Append

stack tables

Merge

join tables

Data visualization

show data as charts

Numerical data

numbers

Categorical data

names or labels

Bar chart

compare groups

Line chart

show trends

Scatter plot

show relationships

Map

show location data

Graph parts

title labels legend

Filters

limit data shown

Slicers

clickable filters

Dashboard

all data in one screen

Infographic

visual way to show info

Contrast

make things stand out

Repetition

keep style the same

Alignment

line things up

Proximity

group related items

Data sourcing

collecting data

Survey

ask people questions

Open ended

long answers

Closed ended

multiple choice

Double barreled

two questions in one

Survey logic

controls question flow

Skip logic

jump questions

Display logic

show certain questions

Population

whole group

Sample

part of group

Random sample

everyone equal chance

Stratified sample

groups sampled evenly

Convenience sample

easy to reach people

Primary data

you collect it

Secondary data

someone else collected it

API

lets systems share data

Robots txt

tells bots what they can access