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

LIMITing results

As you might notice, our database is quite large - about three thousand cars. Sometimes we need to limit our results so only a few rows will be displayed. It may be useful if we work with big data and want to check if our query is valid or when we want to find TOP-n observation based on some condition.

To limit the number of rows to be shown use the LIMIT n statement. For example,


              123
            
SELECT column1, column2
FROM table_name
LIMIT 5

this query will return the first 5 rows from table_name

Завдання

From the audi_cars table extract the first 10 rows of model, price, mileage columns.

Завдання

From the audi_cars table extract the first 10 rows of model, price, mileage columns.

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

Все було зрозуміло?

Секція 1. Розділ 3

LIMITing results

To limit the number of rows to be shown use the LIMIT n statement. For example,


              123
            
SELECT column1, column2
FROM table_name
LIMIT 5

this query will return the first 5 rows from table_name

Завдання

From the audi_cars table extract the first 10 rows of model, price, mileage columns.

Завдання

From the audi_cars table extract the first 10 rows of model, price, mileage columns.

Все було зрозуміло?

Секція 1. Розділ 3

LIMITing results

To limit the number of rows to be shown use the LIMIT n statement. For example,


              123
            
SELECT column1, column2
FROM table_name
LIMIT 5

this query will return the first 5 rows from table_name

Завдання

From the audi_cars table extract the first 10 rows of model, price, mileage columns.

Завдання

From the audi_cars table extract the first 10 rows of model, price, mileage columns.

Все було зрозуміло?

To limit the number of rows to be shown use the LIMIT n statement. For example,


              123
            
SELECT column1, column2
FROM table_name
LIMIT 5

this query will return the first 5 rows from table_name

Завдання

From the audi_cars table extract the first 10 rows of model, price, mileage columns.

Секція 1. Розділ 3