房间数据库中的外键

Question

我正在处理一个结构，其中有几篇文章及其内容存储在两个不同的 tables

首先是文章 table，其中包含如下基本信息：

@Entity(tableName = "Articles")
public class ArticleModel implements Serializable {

    @SerializedName("iArticleID")
    @PrimaryKey(autoGenerate = true)
    public int articleId;

    @ColumnInfo(name = "disciplineId")
    public long disciplineID;

    @SerializedName("tTitle")
    @ColumnInfo(name = "tTitle")
    public String title;

    @SerializedName("file_path")
    @ColumnInfo(name = "article_path")
    public String articlePath;

    @ColumnInfo(name = "lastUpdated")
    public String lastUpdated;

    @ColumnInfo(name = "articleDescription")
    public String articleDescription;

    @ColumnInfo(name = "is_favorite")
    public String isFav = "false";

}

第二个 table 是 FileData，其中包含该文章的内容（文件数据），如下所示

@Entity(foreignKeys = @ForeignKey(entity = FileData.class,
        parentColumns = "article_id",
        childColumns = "iArticleID",
        onDelete = CASCADE))
public class FileData implements Serializable {

    @PrimaryKey(autoGenerate = true)
    private int fileId;

    @ColumnInfo(name = "file_name")
    private String fileName;

    @ColumnInfo(name = "file_path")
    private String filePath;

    @ColumnInfo(name = "content")
    private String content;

    @ColumnInfo(name = "article_id")
    public int aId;

}

我想执行一个内部连接查询，它为我提供了 FilesData 以及文章中的一些列（例如：is_favorite）为此，我尝试使用 FilesData table 中提到的外键约束将 table 与 article_id 相关联。

这是第三个@Embedded class

public class FilesWithArticlesData {

    @Embedded
    ArticleModel articleModel;

    @Embedded
    public FilesData files;

}

内连接查询如下：

 @Query("SELECT FilesData.fileId, FilesData.file_name, FilesData.file_path, FilesData.content,articles.is_favorite FROM files" +
            " INNER JOIN ARTICLES ON articles.articleId = FilesData.article_id  " +
            "WHERE FilesData.content LIKE :searchText")
    public LiveData<List<FilesWithArticlesData>> searchContent(String searchText);

每当我尝试运行应用程序时，我都会收到错误消息

error: (iArticleID) referenced in the foreign key does not exists in the Entity. Available column names:fileId, file_name, file_path, content, article_id

或FOREIGN KEY约束失败

有什么建议..??

Answer 1

您输入了错误的parentColumn

只需更改此

@Entity(foreignKeys = @ForeignKey(entity = ArticleModel.class,
        parentColumns = "iArticleID",
        childColumns = "article_id",
        onDelete = CASCADE))

而不是

@Entity(foreignKeys = @ForeignKey(entity = FileData.class,
        parentColumns = "article_id",
        childColumns = "iArticleID",
        onDelete = CASCADE))

还要更改此

 @SerializedName("iArticleID")
    @PrimaryKey(autoGenerate = true)
    public int articleId;

对此

 @ColumnInfo(name = "iArticleID")
    @PrimaryKey(autoGenerate = true)
    public int articleId;

房间数据库中的外键

ForeignKey in Room Database

database

android

android-room