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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
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.

Taak

Swipe to start coding

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

Oplossing

Switch to desktopSchakel over naar desktop voor praktijkervaringGa verder vanaf waar je bent met een van de onderstaande opties
Was alles duidelijk?

Hoe kunnen we het verbeteren?

Bedankt voor je feedback!

Sectie 3. Hoofdstuk 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.

Taak

Swipe to start coding

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

Oplossing

Switch to desktopSchakel over naar desktop voor praktijkervaringGa verder vanaf waar je bent met een van de onderstaande opties
Was alles duidelijk?

Hoe kunnen we het verbeteren?

Bedankt voor je feedback!

Sectie 3. Hoofdstuk 2
Switch to desktopSchakel over naar desktop voor praktijkervaringGa verder vanaf waar je bent met een van de onderstaande opties
Onze excuses dat er iets mis is gegaan. Wat is er gebeurd?
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