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Databases

Posted by Tej Singh
Tej Singh
Courses Plus Student 2,673 Points

Cant got the problem, Help this statement. (SQL)

QUERY: SELECT * FROM Media JOIN Media_Genres ON Media_Genres.media_id = Genres.genres_id WHERE Media.media_id=3;

Question: We will be writing ONLY the SQL query for this challenge. The library database contains a Media table with the columns media_id, title, img, format, year and category. It also contains a Genres table with the columns genre_id and genre. To join these tables, there is a Media_Genres table that contains the column media_id and genre_id Add to the following SELECT statement to JOIN the Media table and the Genres table using the joining table Media_Genres. SELECT * FROM Media WHERE media_id=3; NOTE: You will need to add the table to the WHERE clause so that the media_id column is not ambiguous.

4 Answers

Tej Singh
Tej Singh
Courses Plus Student 2,673 Points

I've just tried this challenge again and it's a bit confusing. Finally....!

SELECT * FROM Media JOIN Media_Genres ON Media.media_id = Media_Genres.media_id JOIN Genres ON Media_Genres.genre_id = Genres.genre_id WHERE Media_Genres.media_id = 3;

Thanks..

Steven Parker
Steven Parker
231,248 Points
Steven Parker
Steven Parker
231,248 Points

Here's a few hints:

  • when you join the Media_Genres table, you probably want to match just media_id columns
  • you will need a separate JOIN for the Genres table
  • when you join the Genres table, you will probably want to match genre_id columns
Tej Singh
PLUS
Tej Singh
Courses Plus Student 2,673 Points
Tej Singh
Tej Singh
Courses Plus Student 2,673 Points

SELECT * FROM Media JOIN Media_Genres ON Media_Genres.media_id = Genres.genres_id LEFT JOIN Genres ON Genres.genres_id = Media.genres_id WHERE Media.media_id=3;

SQL Error: no such column: Genres.genres_id

Please explain and correct it. Also explain correct query. Step by step.

Oleksii Temchenko
Oleksii Temchenko
3,474 Points
Oleksii Temchenko
Oleksii Temchenko
3,474 Points

I know, that I am quite late with answer, but this what I ended with.

SELECT * FROM Media JOIN Media_Genres ON  Media.media_id = Media_Genres.media_id

//Basically now we have genre_id column in Media, connected with media_id, which are equal in both Media/Media_Genres tables. Also Media and Media_Genres have common media_id and we are obliged to use Media_Genres as joint table.

JOIN Genres ON Genres.genre_id = Media_Genres.genre_id WHERE Media_Genres.media_id = 3

//Now Genres joins the party. We basically adding 1 needed genre (with id=3) to Media table by adding WHERE Clause to 'ON Genres.genre_id = Media_Genres.genre_id', as Media and Media_Genres have common media_id.

This is how we obey the condition that the media_id column should not be ambiguous.

Hope it helps