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SQL Basics
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Course Content

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

bookROUNDing

In the last chapter, you solved the task and received a number with many digits after the decimal place. This is surely precise, but not representative, as there is no way to pay 0.002$, for example. It would be great if we could round numbers to some digits.

Surely it's also implemented into SQL! To round number to n decimal places use ROUND(column_name, n) function. For example, from our audi_cars dataset let's calculate the average price of TT model cars with mileage less than 3000 and round the result to 0 decimals (so it will be an integer).


              
123

            
SELECT ROUND(AVG(price), 0)
FROM audi_cars
WHERE model = 'TT' AND mileage < 3000
copy

That's more representative!

Task

From the audi_cars table calculate the average price for Petrol cars (column fueltype) with Semi-Auto transmission (column transmission). Round the result to 2 digits after the comma.

Switch to desktopSwitch to desktop for real-world practiceContinue from where you are using one of the options below
Everything was clear?

How can we improve it?

Thanks for your feedback!

Section 3. Chapter 4
toggle bottom row

bookROUNDing

In the last chapter, you solved the task and received a number with many digits after the decimal place. This is surely precise, but not representative, as there is no way to pay 0.002$, for example. It would be great if we could round numbers to some digits.

Surely it's also implemented into SQL! To round number to n decimal places use ROUND(column_name, n) function. For example, from our audi_cars dataset let's calculate the average price of TT model cars with mileage less than 3000 and round the result to 0 decimals (so it will be an integer).


              
123

            
SELECT ROUND(AVG(price), 0)
FROM audi_cars
WHERE model = 'TT' AND mileage < 3000
copy

That's more representative!

Task

From the audi_cars table calculate the average price for Petrol cars (column fueltype) with Semi-Auto transmission (column transmission). Round the result to 2 digits after the comma.

Switch to desktopSwitch to desktop for real-world practiceContinue from where you are using one of the options below
Everything was clear?

How can we improve it?

Thanks for your feedback!

Section 3. Chapter 4
toggle bottom row

bookROUNDing

In the last chapter, you solved the task and received a number with many digits after the decimal place. This is surely precise, but not representative, as there is no way to pay 0.002$, for example. It would be great if we could round numbers to some digits.

Surely it's also implemented into SQL! To round number to n decimal places use ROUND(column_name, n) function. For example, from our audi_cars dataset let's calculate the average price of TT model cars with mileage less than 3000 and round the result to 0 decimals (so it will be an integer).


              
123

            
SELECT ROUND(AVG(price), 0)
FROM audi_cars
WHERE model = 'TT' AND mileage < 3000
copy

That's more representative!

Task

From the audi_cars table calculate the average price for Petrol cars (column fueltype) with Semi-Auto transmission (column transmission). Round the result to 2 digits after the comma.

Switch to desktopSwitch to desktop for real-world practiceContinue from where you are using one of the options below
Everything was clear?

How can we improve it?

Thanks for your feedback!

In the last chapter, you solved the task and received a number with many digits after the decimal place. This is surely precise, but not representative, as there is no way to pay 0.002$, for example. It would be great if we could round numbers to some digits.

Surely it's also implemented into SQL! To round number to n decimal places use ROUND(column_name, n) function. For example, from our audi_cars dataset let's calculate the average price of TT model cars with mileage less than 3000 and round the result to 0 decimals (so it will be an integer).


              
123

            
SELECT ROUND(AVG(price), 0)
FROM audi_cars
WHERE model = 'TT' AND mileage < 3000
copy

That's more representative!

Task

From the audi_cars table calculate the average price for Petrol cars (column fueltype) with Semi-Auto transmission (column transmission). Round the result to 2 digits after the comma.

Switch to desktopSwitch to desktop for real-world practiceContinue from where you are using one of the options below
Section 3. Chapter 4
Switch to desktopSwitch to desktop for real-world practiceContinue from where you are using one of the options below
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