Module is.codion.framework.domain
Package is.codion.framework.domain.entity.condition

Interface ForeignKeyCondition

All Superinterfaces:
Condition
public interface ForeignKeyCondition extends Condition
A ForeignKey based condition for filtering entities by their relationships.

ForeignKeyConditions enable querying entities based on their references to other entities. They provide type-safe filtering using entity instances or collections of entities, automatically handling primary key extraction and null value cases.

Foreign key conditions are typically created through the ForeignKey.Factory interface, which all ForeignKey instances implement: 

 // Find albums by specific artist
 Entity aliceInChains = connection.selectSingle(
     Artist.NAME.equalTo("Alice In Chains"));

 List<Entity> aliceInChainsAlbums = connection.select(
     Album.ARTIST_FK.equalTo(aliceInChains));

 // Find tracks by genre
 Entity metalGenre = connection.selectSingle(
     Genre.NAME.equalToIgnoreCase("metal"));

 List<Entity> metalTracks = connection.select(
     Track.GENRE_FK.equalTo(metalGenre));

 // Find albums by multiple artists
 List<Entity> selectedArtists = connection.select(
     Artist.NAME.like("The %"));

 List<Entity> albumsByTheArtists = connection.select(
     Album.ARTIST_FK.in(selectedArtists));

 // Find tracks not in classical playlist
 Long classicalPlaylistId = 1L;
 List<Entity> nonClassicalTracks = connection.select(
     Track.NOT_IN_PLAYLIST.get(Playlist.ID, classicalPlaylistId));

 // Find albums without an artist (orphaned albums)
 List<Entity> orphanedAlbums = connection.select(
     Album.ARTIST_FK.isNull());

 // Find tracks with a genre assigned
 List<Entity> categorizedTracks = connection.select(
     Track.GENRE_FK.isNotNull());

 // Complex query with foreign key conditions
 List<Entity> complexQuery = connection.select(and(
     Album.ARTIST_FK.in(popularArtists),
     Album.ARTIST_FK.notEqualTo(excludedArtist)));

 // Using with Select builder for more control
 List<Entity> detailedQuery = connection.select(
     Select.where(Track.GENRE_FK.equalTo(rockGenre))
         .attributes(Track.NAME, Track.ALBUM_FK)
         .orderBy(ascending(Track.NAME))
         .build());

 // Foreign key conditions with null handling
 List<Entity> albumsWithOrWithoutArtist = connection.select(or(
     Album.ARTIST_FK.equalTo(specificArtist),
     Album.ARTIST_FK.isNull()));
See Also: