--добавление нового столбца с произвольным значением
SELECT
	*,
	'тест' AS test_column
FROM
	books;

--показать если книга написана на английском
SELECT
	title,
	language_code,
	language_code = 'eng' AS English_book
FROM
	books;

--операторы сравнения
SELECT
	title,
	num_pages,
	num_pages > 652 AS more_than_652,
	num_pages >= 652 AS more_and_equal_than_652,
	average_rating,
	average_rating < 4.38 AS "less_than_4.38",
	average_rating <= 3.74 AS "less_and_equal_than_3.74",
	authors,
	authors != 'J.K. Rowling' AS not_rowling,
	authors <> 'J.K. Rowling' AS not_rowling2
FROM
	books;

--операторы сравнения вместе с сортировкой
SELECT
	title,
	average_rating,
	average_rating <= 4.38 AS "less_than_4.38"
FROM
	books
ORDER BY
	"less_than_4.38" ASC;

--Напишите запрос, который получает сумму всех оценок книги (сумма всех оценок = средняя оценка (average_rating) * количество оценок(ratings_count)) из таблицы books.

SELECT
	average_rating * ratings_count AS grades
FROM
	books;