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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

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Grouping by multiple columns

Can we group observations based on multiple columns? For example, we can group all cars by year and engine size and find the most expensive within these.

To group by multiple columns use the same approach as for sorting by multiple columns: just put it within GROUP BY statement separated with a comma. The query for the example above will look like this:


              
123

            
SELECT year, enginesize, AVG(price)
FROM audi_cars
GROUP BY year, enginesize
copy
Opgave

Swipe to start coding

From the audi_cars table calculate the maximum, average, and minimum price for each model manufactured in different years.

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 5. Kapitel 3
toggle bottom row

book
Grouping by multiple columns

Can we group observations based on multiple columns? For example, we can group all cars by year and engine size and find the most expensive within these.

To group by multiple columns use the same approach as for sorting by multiple columns: just put it within GROUP BY statement separated with a comma. The query for the example above will look like this:


              
123

            
SELECT year, enginesize, AVG(price)
FROM audi_cars
GROUP BY year, enginesize
copy
Opgave

Swipe to start coding

From the audi_cars table calculate the maximum, average, and minimum price for each model manufactured in different years.

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 5. 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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