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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
Number filtering

But what if we want to choose a car with small mileage, let it be less than 5000 miles. We need to set the condition to a numeric column.

This also can be done with WHERE statement. For example,


              
123

            
SELECT *
FROM audi_cars
WHERE mileage < 5000
copy

Comparison operators you also can use for numeric columns:

  • < - less than
  • <= - less-equal
  • >= - greater-equal -> - greater
  • = - equal
  • <> - not equal.

Now let's try to find the cheapest car in this dataset.

Opgave

Swipe to start coding

From the audi_cars dataset extract cars with price less than 10 000.

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 2. Kapitel 2
toggle bottom row

book
Number filtering

But what if we want to choose a car with small mileage, let it be less than 5000 miles. We need to set the condition to a numeric column.

This also can be done with WHERE statement. For example,


              
123

            
SELECT *
FROM audi_cars
WHERE mileage < 5000
copy

Comparison operators you also can use for numeric columns:

  • < - less than
  • <= - less-equal
  • >= - greater-equal -> - greater
  • = - equal
  • <> - not equal.

Now let's try to find the cheapest car in this dataset.

Opgave

Swipe to start coding

From the audi_cars dataset extract cars with price less than 10 000.

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 2. Kapitel 2
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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