【SQL】SQL训练网站 SQLBlot

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网站地址：

https://sqlbolt.com/

Lesson1:

-- https://sqlbolt.com/lesson/select_queries_introduction

-- Find the title of each film ✓
SELECT `TITLE ` FROM `movies`;

-- Find the director of each film ✓
SELECT `DIRECTOR` FROM movies;

-- Find the title and director of each film ✓
SELECT `TITLE`,`DIRECTOR` FROM movies;

-- Find the title and year of each film ✓
SELECT `TITLE`,`YEAR` FROM movies;

-- Find all the information about each film ✓
SELECT * FROM movies;

Lesson2:

-- https://sqlbolt.com/lesson/select_queries_with_constraints

-- Find the movie with a row id of 6 ✓
SELECT * FROM movies WHERE `ID` = 6;

-- Find the movies not released in the years between 2000 and 2010 ✓
SELECT * FROM movies WHERE `YEAR` BETWEEN 2000 AND 2010;

-- Find the movies not released in the years between 2000 and 2010 ✓
SELECT `TITLE`, `YEAR` FROM movies WHERE `YEAR` < 2000 OR `YEAR` > 2010;
SELECT * FROM movies WHERE `YEAR` NOT BETWEEN 2000 AND 2010;

-- Find the first 5 Pixar movies and their release year ✓
SELECT `TITLE`, `YEAR` FROM movies WHERE `YEAR` <= 2003;

Lesson3:

https://sqlbolt.com/lesson/select_queries_with_constraints_pt_2

-- Find all the Toy Story movies ✓
SELECT * FROM movies WHERE `TITLE ` LIKE '%Toy Story%';

-- Find all the movies directed by John Lasseter ✓
SELECT * FROM movies WHERE `DIRECTOR` = 'John Lasseter'

-- Find all the movies (and director) not directed by John Lasseter ✓
SELECT * FROM movies WHERE `DIRECTOR` != 'John Lasseter'

-- Find all the WALL-* movies ✓
SELECT * FROM movies WHERE `TITLE` LIKE '%WALL-%'

Lesson4:

-- https://sqlbolt.com/lesson/filtering_sorting_query_results

-- List all directors of Pixar movies (alphabetically), without duplicates ✓
SELECT DISTINCT `DIRECTOR` FROM movies ORDER BY `DIRECTOR`

-- List the last four Pixar movies released (ordered from most recent to least) ✓
SELECT * FROM movies ORDER BY `YEAR` DESC LIMIT 4

-- List the first five Pixar movies sorted alphabetically ✓
SELECT * FROM movies ORDER BY `TITLE` ASC LIMIT 5

-- List the next five Pixar movies sorted alphabetically ✓
SELECT * FROM movies ORDER BY `TITLE` ASC LIMIT 5, 5

Lesson5:

-- https://sqlbolt.com/lesson/select_queries_review

-- List all the Canadian cities and their populations ✓
SELECT * FROM north_american_cities WHERE `COUNTRY` = 'Canada';

-- Order all the cities in the United States by their latitude from north to south ✓
SELECT * FROM north_american_cities 
WHERE `COUNTRY` = 'United States' 
ORDER BY `LATITUDE` DESC;

-- List all the cities west of Chicago, ordered from west to east ✓
SELECT `CITY`,`LONGTITUDE` FROM north_american_cities
WHERE `LONGTITUDE` < -87.629798
ORDER BY `LONGTITUDE` ASC;

-- List the two largest cities in Mexico (by population) ✓
SELECT * FROM north_american_cities 
WHERE `COUNTRY` = 'Mexico' 
ORDER BY `POPULATION` DESC LIMIT 2

-- List the third and fourth largest cities (by population) in the United States and their population ✓
SELECT * FROM north_american_cities 
WHERE `COUNTRY` = 'United States' 
ORDER BY `POPULATION` DESC LIMIT 2, 2

Lesson6:

-- https://sqlbolt.com/lesson/select_queries_with_joins

-- Find the domestic and international sales for each movie ✓
SELECT 
    A.*,
    B.`DOMESTIC_SALES`,
    B.`INTERNATIONAL_SALES`
FROM 
    movies AS A
    JOIN `boxoffice` AS B ON A.ID = B.MOVIE_ID;

-- Show the sales numbers for each movie that did better internationally rather than domestically ✓
SELECT `title`, `domestic_sales`, `international_sales`
FROM 
　　`MOVIES` AS A
　　JOIN `BOXOFFICE` AS B ON A.id = B.movie_id
WHERE B.`international_sales ` > B.`domestic_sales`;

-- List all the movies by their ratings in descending order ✓
SELECT A.`title`, B.`rating`
FROM 
    `movies` AS A
    JOIN `boxoffice` AS B ON movies.id = boxoffice.movie_id
ORDER BY rating DESC;

Lesson7:

-- https://sqlbolt.com/lesson/select_queries_with_outer_joins

-- Find the list of all buildings that have employees ✓
SELECT DISTINCT building FROM employees;

-- Find the list of all buildings and their capacity ✓
SELECT * FROM Buildings 

-- List all buildings and the distinct employee roles in each building (including empty buildings) ✓
SELECT DISTINCT A.`building_name`, B.`role `
FROM 
    buildings AS A
    LEFT JOIN employees AS B ON A.building_name = B.building;

Lesson8:

-- https://sqlbolt.com/lesson/select_queries_with_nulls

-- Find the name and role of all employees who have not been assigned to a building ✓
SELECT * FROM Employees WHERE Building IS NULL

-- Find the names of the buildings that hold no employees ✓
SELECT
  A.Building_name
FROM
  Buildings AS A
  LEFT JOIN Employees AS B ON A.Building_name = B.Building
WHERE
  B.Building IS NULL

Lesson9:

-- https://sqlbolt.com/lesson/select_queries_with_expressions

-- List all movies and their combined sales in millions of dollars ✓
SELECT 
  A.title, 
  (domestic_sales + international_sales) / 1000000 AS gross_sales_millions
FROM 
  movies AS A,
  JOIN boxoffice AS B ON A.id = B.movie_id;

-- List all movies and their ratings in percent ✓
SELECT 
  A.TITLE,
	B.RATING * 10 AS rating_percent
FROM 
  movies AS A
  JOIN Boxoffice AS B ON A.ID = B.MOVIE_ID

-- List all movies that were released on even number years ✓
SELECT title, year
FROM movies
WHERE year % 2 = 0;

Lesson10:

-- https://sqlbolt.com/lesson/select_queries_with_aggregates

-- Find the longest time that an employee has been at the studio ✓
SELECT * FROM employees ORDER BY Years_employed DESC LIMIT 1;

-- For each role, find the average number of years employed by employees in that role ✓
SELECT ROLE, AVG(Years_employed) FROM Employees GROUP BY ROLE

-- Find the total number of employee years worked in each building ✓
SELECT building, SUM(years_employed) as Total_years_employed
FROM employees
GROUP BY building;

Lesson11:

-- https://sqlbolt.com/lesson/select_queries_with_aggregates_pt_2

--Find the number of Artists in the studio (without a HAVING clause) ✓
SELECT ROLE, COUNT(NAME) 
FROM employees 
WHERE ROLE = 'Artist' 
GROUP BY ROLE;

SELECT role, COUNT(*) as Number_of_artists
FROM employees
WHERE role = "Artist";

-- Find the number of Employees of each role in the studio ✓
SELECT role, COUNT(*) as Number_of_artists
FROM employees
GROUP BY ROLE

-- Find the total number of years employed by all Engineers ✓
SELECT SUM(Years_employed) FROM Employees WHERE ROLE = 'Engineer';

Lesson12:

-- https://sqlbolt.com/lesson/select_queries_order_of_execution

-- Find the number of movies each director has directed ✓
SELECT Director,COUNT(*) FROM movies GROUP BY Director;

-- Find the total domestic and international sales that can be attributed to each director ✓
SELECT 
  Director,
  SUM(B.Domestic_sales + B.International_sales) AS Cumulative_sales_from_all_movies
FROM
  Movies AS A
  JOIN Boxoffice AS B ON A.ID = B.MOVIE_ID
GROUP BY A.Director

Lesson13:

-- https://sqlbolt.com/lesson/inserting_rows

-- Add the studio's new production, Toy Story 4 to the list of movies (you can use any director) ✓
INSERT INTO Movies (Id, Title, Director, Year, Length_minutes) VALUES
(NULL, 'Toy Story 4', 'John Lasseter', NULL, NULL)

-- Toy Story 4 has been released to critical acclaim! It had a rating of 8.7, and made 340 million domestically and 270 million internationally. Add the record to the BoxOffice table. ✓
INSERT INTO Boxoffice (Movie_id, Rating, Domestic_sales, International_sales) VALUES
(15, ' 8.7', 34000000, 27000000)

Lesson14:

-- https://sqlbolt.com/lesson/updating_rows

-- The director for A Bug's Life is incorrect, it was actually directed by John Lasseter ✓
UPDATE `Movies` 
SET DIRECTOR = 'John Lasseter'
WHERE TITLE = "A Bug's Life" 

-- The year that Toy Story 2 was released is incorrect, it was actually released in 1999 ✓
UPDATE `Movies` 
SET YEAR = 1999
WHERE TITLE = 'Toy Story 2'

-- Both the title and director for Toy Story 8 is incorrect! The title should be "Toy Story 3" and it was directed by Lee Unkrich ✓
UPDATE `Movies`
SET 
  DIRECTOR = 'Lee Unkrich',
  TITLE = 'Toy Story 3'
WHERE TITLE = 'Toy Story 8'

Lesson15:

-- https://sqlbolt.com/lesson/deleting_rows

-- This database is getting too big, lets remove all movies that were released before 2005. ✓
DELETE FROM movies WHERE YEAR < 2005;

-- Andrew Stanton has also left the studio, so please remove all movies directed by him. ✓
DELETE FROM movies WHERE DIRECTOR = 'Andrew Stanton';

Lesson16:

-- https://sqlbolt.com/lesson/creating_tables

-- Create a new table named Database with the following columns:
– Name A string (text) describing the name of the database
– Version A number (floating point) of the latest version of this database
– Download_count An integer count of the number of times this database was downloaded
This table has no constraints.

CREATE TABLE `Database`(
	NAME VARCHAR,
	VERSION FLOAT,
	Download_count INT
)

Lesson17:

-- Add a column named Aspect_ratio with a FLOAT data type to store the aspect-ratio each movie was released in. ✓
ALTER TABLE `Movies`
ADD COLUMN `Aspect_ratio` FLOAT DEFAULT 2.39

-- Add another column named Language with a TEXT data type to store the language that the movie was released in. Ensure that the default for this language is English. ✓
ALTER TABLE `Movies`
ADD COLUMN `Language` TEXT DEFAULT "English";

Lesson18:

-- https://sqlbolt.com/lesson/dropping_tables

-- We've sadly reached the end of our lessons, lets clean up by removing the Movies table ✓
DROP TABLE `MOVIES`;

-- And drop the BoxOffice table as well ✓
DROP TABLE `BOXOFFICE`;

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