Зміст курсу

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

Aliases

The outputs of the last two tasks were single columns with single values. If you noticed, this column had a name count, which is not, to be honest representative. Seems like it's only a matter of taste. But in the future, when you will work with multiple tables, will join one table to another, the same names will be a huge problem. Even from the point of interpreting the data.

In SQL you can easily declare a new name to a column by using AS statement. For example,


              12
            
SELECT COUNT(DISTINCT(country)) AS "number of countries"
FROM visitors

This query will return a single value in the single column named number of countries, which is much readable than count.

Please note, that the aliases you use must be placed within double-quotes. Using single quotes will result in SQL error!

Завдання

Extract unique types of fuel consumed by cars (column fueltype) and name this column as "Fuel type".

Перейдіть на комп'ютер для реальної практикиПродовжуйте з того місця, де ви зупинились, використовуючи один з наведених нижче варіантів

Все було зрозуміло?

Дякуємо за ваш відгук!

Секція 1. Розділ 8

Aliases

In SQL you can easily declare a new name to a column by using AS statement. For example,


              12
            
SELECT COUNT(DISTINCT(country)) AS "number of countries"
FROM visitors

This query will return a single value in the single column named number of countries, which is much readable than count.

Please note, that the aliases you use must be placed within double-quotes. Using single quotes will result in SQL error!

Завдання

Extract unique types of fuel consumed by cars (column fueltype) and name this column as "Fuel type".

Все було зрозуміло?

Дякуємо за ваш відгук!

Секція 1. Розділ 8

Aliases

In SQL you can easily declare a new name to a column by using AS statement. For example,


              12
            
SELECT COUNT(DISTINCT(country)) AS "number of countries"
FROM visitors

This query will return a single value in the single column named number of countries, which is much readable than count.

Please note, that the aliases you use must be placed within double-quotes. Using single quotes will result in SQL error!

Завдання

Extract unique types of fuel consumed by cars (column fueltype) and name this column as "Fuel type".

Все було зрозуміло?

Дякуємо за ваш відгук!

In SQL you can easily declare a new name to a column by using AS statement. For example,


              12
            
SELECT COUNT(DISTINCT(country)) AS "number of countries"
FROM visitors

This query will return a single value in the single column named number of countries, which is much readable than count.

Please note, that the aliases you use must be placed within double-quotes. Using single quotes will result in SQL error!

Завдання

Extract unique types of fuel consumed by cars (column fueltype) and name this column as "Fuel type".

Секція 1. Розділ 8