Question

I’m working with the Android SQLite Database and I have two Tables in it.

Table CHECKPOINTS defines a foreign key to an attribute in Table TOUR.

After storing data to the database the table Tour is displayed correctly. But, the column with the foreign key TOUR_ID in table CHECKPOINTS remains blank. I don’t know why.

The syntax should be ok and I also set the PRAGMA foreign_keys = ON;.
After experimenting a while I defined a Trigger in the onCreate() function of my DatabaseHelper.

But, now I get an Error:

android.database.CursorIndexOutOfBoundsException: Index 0 requested, with a size of 0.

DatabaseHelper:

private static final String TABLE_CREATE_TOUR = "create table TOUR("
        + " ID integer primary key autoincrement, "
        + " NAME varchar(20)) ";


private static final String TABLE_CREATE_CHECKPOINT = "create table CHECKPOINT("
        + " ID integer primary key autoincrement, "
        + " TOUR_ID integer not null, "
        + " FOREIGN KEY (TOUR_ID) REFERENCES TOUR(ID)) ";


public void onCreate(SQLiteDatabase database) {
    database.execSQL(TABLE_CREATE_TOUR);
    database.execSQL(TABLE_CREATE_CHECKPOINT);

    database.execSQL("CREATE TRIGGER fk_checkpoint_tourid BEFORE INSERT ON CHECKPOINT "
                    + " FOR EACH ROW BEGIN "
                    + " SELECT CASE WHEN ((SELECT ID FROM TOUR WHERE ID = new.TOUR_ID ) IS NULL) "
                    + " THEN RAISE (ABORT, 'Foreign Key Violation') END; "
                    + " END;");

}

DataSource:

public void open() throws SQLException {
    database = dbhelper.getWritableDatabase();

    // Enable foreign key constraints
    if (!database.isReadOnly()) {
         database.execSQL("PRAGMA foreign_keys = ON;");
    } 
}

Does anyone have an idea, on how to get this thing going ?

EDIT:

Insert in Table TOUR:

    public long InsertTour(String name){
    ContentValues values = new ContentValues();
    values.put("NAME", name);

    return database.insert("TOUR", null, values);       
}

The Table CHECKPOINT contains more data as described above. Here’s the insert:

public Entry createEntry(String PARAM1, String PARAM2, long PARAM3, String PARAM4) {
    ContentValues values = new ContentValues();
    values.put("COLUMN1", PARAM1);
    values.put("COLUMN2", PARAM2);
    values.put("COLUMN3", PARAM3);
    values.put("COLUMN4", PARAM4);

    long insertId = database.insert("CHECKPOINT", null, values);

    Cursor cursor = database.query("CHECKPOINT", allColumns, "ID = " + insertId, null, null, null, null);
    cursor.moveToFirst();

    return cursorToEntry(cursor);
}

Answer 1

It’s somewhat difficult to tell what’s wrong because you are not giving the complete details but from your answers I think you have the wrong concept about foreign keys and you are expecting something to be automatically “filled via foreign key“.

Foreign key constraints are used to enforce exists relationships between tables. That is, you would not be able to insert a checkpoint row having a tour_id that doesn’t exist on tour table.

Read more at http://www.sqlite.org/foreignkeys.html