Join 3 tables in SQLite database

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陌清茗
陌清茗 2021-01-31 09:34

I have 3 tables in SQLite database:

Songs:

_id | name | length | artist_id (foreign key) | album_id (foreign key)

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  • 2021-01-31 09:59

    Using an explicit JOIN instead of an implicit one, the following should get what you want, although it is curious that your implicit join syntax did not return correct results in the first place. I have used a LEFT JOIN, to account for songs which do not have an associated artist or album, but that may not be necessary for your data set and an INNER JOIN could be used instead.

    I have also added column aliases to eliminate ambiguity when fetching rows, since you have similar column names in most of your tables (id, name).

    SELECT
      Songs._id AS song_id,
      Songs.name AS song_name, 
      Songs.length, 
      Songs.artist_id AS artist_id, 
      Artists.name AS artist_name, 
      Songs.album_id AS album_id, 
      Albums.name AS album_name
    FROM 
     Songs 
     LEFT JOIN Artists ON Songs.artist_id = Artists._id
     LEFT JOIN Albums ON Songs.album_id = Albums._id
    
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  • 2021-01-31 09:59

    Try this select, may by the Artists is more important than others, so the Songs come trough Artists and Albums from Songs.

    SELECT
      Songs._id AS song_id,
      Songs.name AS song_name, 
      Songs.length, 
      Songs.artist_id AS artist_id, 
      Artists.name AS artist_name, 
      Songs.album_id AS album_id, 
      Albums.name AS album_name
    FROM 
     Artists
     LEFT JOIN Songs ON Songs.artist_id = Artists._id
     LEFT JOIN Albums ON Songs.album_id = Albums._id
    

    Also if there is no entry in Songs belonging to a particular artist or no entry in Albums belonging to a particular song, you will still get the artist entry thanks to the LEFT JOIN. If you would like to return only artists with songs and albums, use JOIN instead.

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  • 2021-01-31 10:13

    try sql inner join

               inner join Artists on Songs.artist_id = Artists._id
    
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