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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
SUMming values

There is one more function that has to be implemented - function for summing values. For example, we may want to calculate the total revenue for a certain item.

To sum values in column use SUM function followed by column which values you want to sum. For our abstract example,


              
123

            
SELECT SUM(revenue)
FROM sells
WHERE item = 'Sofa'
copy

Please note, that SUM function works only with numeric columns.

Opgave

Swipe to start coding

From the audi_cars table calculate the total tax for all RS4 cars.

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 2
toggle bottom row

book
SUMming values

There is one more function that has to be implemented - function for summing values. For example, we may want to calculate the total revenue for a certain item.

To sum values in column use SUM function followed by column which values you want to sum. For our abstract example,


              
123

            
SELECT SUM(revenue)
FROM sells
WHERE item = 'Sofa'
copy

Please note, that SUM function works only with numeric columns.

Opgave

Swipe to start coding

From the audi_cars table calculate the total tax for all RS4 cars.

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 2
Switch to desktopSkift til skrivebord for at øve i den virkelige verdenFortsæt der, hvor du er, med en af nedenstående muligheder
Vi beklager, at noget gik galt. Hvad skete der?
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