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

LIKE filtering

Sometimes you need to filter by some non-numeric column, but not by exact value, but some pattern.

One of the clearest examples is filtering emails so only emails hosted on google will be left (@gmail.com). In SQL it can be done by using LIKE statement and pattern built by using some wildcards. The most common wildcards are:

% - represents zero, one or more symbols
_ - represents one, and only one symbol.

For example, pattern a% will match everything starting with a (even single symbol a), pattern _B will match only two-letters strings ending with B.

To solve the task above we can use pattern %@gmail.com, as there is usually more than one symbol before @ symbol, but we don't know the exact number.


              123
            
SELECT *
FROM visitors
WHERE email LIKE '%@gmail.com'

Please note, that you need to place your pattern within single quotes!

Завдання

From the audi_cars table extract all the A-series cars (model starts with the letter A).

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 2. Розділ 6

LIKE filtering

Sometimes you need to filter by some non-numeric column, but not by exact value, but some pattern.

% - represents zero, one or more symbols
_ - represents one, and only one symbol.

For example, pattern a% will match everything starting with a (even single symbol a), pattern _B will match only two-letters strings ending with B.

To solve the task above we can use pattern %@gmail.com, as there is usually more than one symbol before @ symbol, but we don't know the exact number.


              123
            
SELECT *
FROM visitors
WHERE email LIKE '%@gmail.com'

Please note, that you need to place your pattern within single quotes!

Завдання

From the audi_cars table extract all the A-series cars (model starts with the letter A).

Все було зрозуміло?

Дякуємо за ваш відгук!

Секція 2. Розділ 6

LIKE filtering

Sometimes you need to filter by some non-numeric column, but not by exact value, but some pattern.

% - represents zero, one or more symbols
_ - represents one, and only one symbol.

For example, pattern a% will match everything starting with a (even single symbol a), pattern _B will match only two-letters strings ending with B.

To solve the task above we can use pattern %@gmail.com, as there is usually more than one symbol before @ symbol, but we don't know the exact number.


              123
            
SELECT *
FROM visitors
WHERE email LIKE '%@gmail.com'

Please note, that you need to place your pattern within single quotes!

Завдання

From the audi_cars table extract all the A-series cars (model starts with the letter A).

Все було зрозуміло?

Дякуємо за ваш відгук!

Sometimes you need to filter by some non-numeric column, but not by exact value, but some pattern.

% - represents zero, one or more symbols
_ - represents one, and only one symbol.

For example, pattern a% will match everything starting with a (even single symbol a), pattern _B will match only two-letters strings ending with B.

To solve the task above we can use pattern %@gmail.com, as there is usually more than one symbol before @ symbol, but we don't know the exact number.


              123
            
SELECT *
FROM visitors
WHERE email LIKE '%@gmail.com'

Please note, that you need to place your pattern within single quotes!

Завдання

From the audi_cars table extract all the A-series cars (model starts with the letter A).

Секція 2. Розділ 6