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SQL Basics
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Kursusindhold

SQL Basics

SQL Basics

1. Selecting
The very first meet with the databaseSELECTing certain columnsLIMITing resultsUnique values from columnUnique values from multiple columnsHow many?How many unique?AliasesTables aliases
2. Filtering
Word filteringNumber filteringCombining conditionsFiltering by numeric intervalMultiple filtering on one columnLIKE filteringNOT like this!
3. Aggregating
MINimal and MAXimal valuesSUMming valuesMean valuesROUNDing
4. Sorting
Sorting by one columnSorting in DESCending orderThe cheapest carSorting by multiple columns
5. Grouping
What is grouping?More aggregate statistics!Grouping by multiple columnsThe cheapest combinationHAVING some conditionsLeast consuming carsFiltering group size
6. Practicing
Challenge: Unique combinationsChallenge: Average Q-series cars priceChallenge: The cheapest new A-series carsChallenge: Relation between engine size and fuel consumptionChallenge: Mileage and manufacture year - is there relation?Challenge: Average price for each model and yearChallenge: The most expensive transmission + engine size combinations

book
Mean values

The next function we will talk about - is mean. Mean (average) is probably one of the most simple and usable statistics in real life.

For example, for our audi_cars table, we can calculate the average mileage for cars manufactured in 2020. To calculate the average use AVG function followed by column name.


              
123

            
SELECT AVG(mileage)
FROM audi_cars
WHERE year = 2020
copy
Opgave

Swipe to start coding

Using table audi_cars calculate the average price of the A4 model manufactured in 2018.

Løsning

Switch to desktopSkift til skrivebord for at øve i den virkelige verdenFortsæt der, hvor du er, med en af nedenstående muligheder
Var alt klart?

Hvordan kan vi forbedre det?

Tak for dine kommentarer!

Sektion 3. Kapitel 3
toggle bottom row

book
Mean values

The next function we will talk about - is mean. Mean (average) is probably one of the most simple and usable statistics in real life.

For example, for our audi_cars table, we can calculate the average mileage for cars manufactured in 2020. To calculate the average use AVG function followed by column name.


              
123

            
SELECT AVG(mileage)
FROM audi_cars
WHERE year = 2020
copy
Opgave

Swipe to start coding

Using table audi_cars calculate the average price of the A4 model manufactured in 2018.

Løsning

Switch to desktopSkift til skrivebord for at øve i den virkelige verdenFortsæt der, hvor du er, med en af nedenstående muligheder
Var alt klart?

Hvordan kan vi forbedre det?

Tak for dine kommentarer!

Sektion 3. Kapitel 3
Switch to desktopSkift til skrivebord for at øve i den virkelige verdenFortsæt der, hvor du er, med en af nedenstående muligheder
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