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SQL Basics
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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
SELECTing certain columns

Let's dig into our database. This database has 9 columns:

  1. model - model of the car
  2. year - year of manufacture
  3. price - car price in Euros
  4. transmission - type of gearbox
  5. mileage - miles drove
  6. fueltype - engine fuel type
  7. tax - road tax
  8. mpg - miles per gallon
  9. enginesize - engine size in liters.

To extract certain columns you need to select them by their names, like:


              
12

            
SELECT column1, column2, column3
FROM table_name
copy

Please note, that SQL is also case-insensitive to column names, i.e. if the column has name id both notations id and ID will be interpreted the same.

Opgave

Swipe to start coding

Extract columns model, year, and price from the audi_cars database.

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 1. Kapitel 2
toggle bottom row

book
SELECTing certain columns

Let's dig into our database. This database has 9 columns:

  1. model - model of the car
  2. year - year of manufacture
  3. price - car price in Euros
  4. transmission - type of gearbox
  5. mileage - miles drove
  6. fueltype - engine fuel type
  7. tax - road tax
  8. mpg - miles per gallon
  9. enginesize - engine size in liters.

To extract certain columns you need to select them by their names, like:


              
12

            
SELECT column1, column2, column3
FROM table_name
copy

Please note, that SQL is also case-insensitive to column names, i.e. if the column has name id both notations id and ID will be interpreted the same.

Opgave

Swipe to start coding

Extract columns model, year, and price from the audi_cars database.

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 1. 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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