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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
MINimal and MAXimal values

Now it's time to talk about aggregate functions - functions that calculate some summary stats. Let's start with extremal summary stats - minimum and maximum values.

To find the minimum (or maximum) value in the column use MIN (or MAX) functions followed by column name. For example, we can find out the cheapest car with Automatic transmission.


              
123

            
SELECT MIN(price)
FROM audi_cars
WHERE transmission = 'Automatic'
copy

Please note, that unlike for DISTINCT function you need to use parentheses for MIN and MAX functions.

Opgave

Swipe to start coding

From the audi_cars table find out the price of the most expensive Diesel car (fueltype column).

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 1
toggle bottom row

book
MINimal and MAXimal values

Now it's time to talk about aggregate functions - functions that calculate some summary stats. Let's start with extremal summary stats - minimum and maximum values.

To find the minimum (or maximum) value in the column use MIN (or MAX) functions followed by column name. For example, we can find out the cheapest car with Automatic transmission.


              
123

            
SELECT MIN(price)
FROM audi_cars
WHERE transmission = 'Automatic'
copy

Please note, that unlike for DISTINCT function you need to use parentheses for MIN and MAX functions.

Opgave

Swipe to start coding

From the audi_cars table find out the price of the most expensive Diesel car (fueltype column).

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 1
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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