Course Content

SQL Basics

1. Selecting

The very first meet with the database SELECTing certain columns LIMITing results Unique values from column Unique values from multiple columns How many?How many unique?Aliases Tables aliases

2. Filtering

Word filtering Number filtering Combining conditions Filtering by numeric interval Multiple filtering on one column LIKE filtering NOT like this!

3. Aggregating

MINimal and MAXimal values SUMming values Mean values ROUNDing

4. Sorting

Sorting by one column Sorting in DESCending order The cheapest car Sorting by multiple columns

5. Grouping

What is grouping?More aggregate statistics!Grouping by multiple columns The cheapest combination HAVING some conditions Least consuming cars Filtering group size

6. Practicing

Challenge: Unique combinations Challenge: Average Q-series cars price Challenge: The cheapest new A-series cars Challenge: Relation between engine size and fuel consumption Challenge: Mileage and manufacture year - is there relation?Challenge: Average price for each model and year Challenge: The most expensive transmission + engine size combinations

ROUNDing

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

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.

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 desktop for real-world practiceContinue from where you are using one of the options below

Everything was clear?

Section 3. Chapter 4

ROUNDing


              123
            
SELECT ROUND(AVG(price), 0)
FROM audi_cars
WHERE model = 'TT' AND mileage < 3000

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.

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 desktop for real-world practiceContinue from where you are using one of the options below

Everything was clear?

Section 3. Chapter 4

ROUNDing


              123
            
SELECT ROUND(AVG(price), 0)
FROM audi_cars
WHERE model = 'TT' AND mileage < 3000

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.

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 desktop for real-world practiceContinue from where you are using one of the options below

Everything was clear?


              123
            
SELECT ROUND(AVG(price), 0)
FROM audi_cars
WHERE model = 'TT' AND mileage < 3000

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 desktop for real-world practiceContinue from where you are using one of the options below

Section 3. Chapter 4

Switch to desktop for real-world practiceContinue from where you are using one of the options below