Android的SQLite外鍵不工作

我試圖創建2表之間的關係，但FK不填充。它保持爲空。以下是我的代碼Android的SQLite外鍵不工作

public static final int DATABASE_VERSION = 1; 
// Database Name 
public static final String DATABASE_NAME = "LocalRugbyDB.db"; 

//table names 
public static final String TABLE_PLAYER_INFO = "PLAYER_Local"; 
public static final String TABLE_TEAM_INFO = "TEAM_local"; 

//add fields to player table 
public static final String KEY_PLAYER_ID = "_id"; 
public static final String KEY_FNAME = "first_name"; 
public static final String KEY_LNAME = "last_name"; 
public static final String KEY_AGE = "age"; 
public static final String KEY_HEIGHT = "height"; 
public static final String KEY_WEIGHT = "weight"; 
public static final String KEY_POSITION = "position"; 
public static final String KEY_TEAM = "team"; 
public static final String TEAM_ID = "team_id"; 

// add field to team table 
public static final String KEY_TEAM_ID = "_id"; 
public static final String KEY_TEAMNAME = "team_name"; 

public MySQLiteHelper(Context context, String name, 
     CursorFactory factory, int version) { 
    super(context, DATABASE_NAME, null, DATABASE_VERSION); 
    Log.i("onCreateMaybe", "Created"); 
} 

@Override 
public void onCreate(SQLiteDatabase db) { 
    // SQL statement to create book table 
    String CREATE_PLAYER_TABLE = "CREATE TABLE " + TABLE_PLAYER_INFO + "(" 
      + KEY_PLAYER_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " 
      + KEY_FNAME + " TEXT," 
      + KEY_LNAME + " TEXT," 
      + KEY_POSITION + " TEXT," 
      + KEY_HEIGHT + " TEXT," 
      + KEY_AGE + " TEXT," 
      + KEY_WEIGHT + " TEXT," 
      + KEY_TEAM + " TEXT," 
      + TEAM_ID + " integer," 
      + " FOREIGN KEY ("+TEAM_ID+") REFERENCES "+TABLE_TEAM_INFO+" ("+KEY_TEAM_ID+"));"; 


    String CREATE_TEAM_TABLE = "CREATE TABLE " + TABLE_TEAM_INFO + "(" 
      + KEY_TEAM_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " 
      + KEY_TEAMNAME + " TEXT" + ");"; 

    // create books table 
    db.execSQL("PRAGMA foreign_keys = ON;"); 
    db.execSQL(CREATE_TEAM_TABLE); 
    db.execSQL(CREATE_PLAYER_TABLE); 

}

這裏您可以看到FK列（team_id）未被填充。我沒有得到任何錯誤，並試圖解決這個問題好幾個小時。 enter image description here

來源

2013-12-14 Chris Mowbray

你是如何將這些數據？當我這樣做時，我首先創建「外部」行（團隊），並使用生成的FK，然後將行插入從屬表（播放器）中。有可能有這樣做的狡猾的方式，但這是有效的。另外，您可能會添加一些限定符以防止FK爲空。 –

外鍵是確保數據庫保持一致的機制;他們做而不是自動查找其他表中的值。

你還得自己做所有的工作。唯一的區別是數據庫將阻止您進行不一致的更改。

您的數據庫未正確歸一化;球隊名稱在所有球員記錄中都是重複的。只需從播放器表中放下KEY_TEAM即可。

要插入與正確的團隊ID一個新的球員，你可以使用這樣的代碼：

long lookupOrCreateTeamID(String name) { 
    Cursor c = db.query(TABLE_TEAM_INFO, new String[] { KEY_TEAM_ID }, 
         KEY_TEAMNAME + " = ?", new String[] { name }, 
         null, null, null); 
    if (c.moveToFirst()) 
     return c.getLong(0); 
    else { 
     ContentValues cv = new ContentValues(); 
     cv.put(KEY_TEAMNAME, name); 
     return db.insert(TABLE_TEAM_INFO, null, cv); 
    } 
} 

long createPlayer(String firstName, ..., String teamName) { 
    ContentValues cv = new ContentValues(); 
    cv.put(KEY_FNAME, firstName); 
    ... 
    cv.put(TEAM_ID, lookupOrCreateTeamID(teamName)); 
    return db.insert(TABLE_PLAYER_INFO, null, cv); 
}

請注意，PRAGMA foreign_keys必須再次執行對打開每一個連接數據庫。所以，你不應該在onCreate但在onConfigure做到這一點（如果你使用的API級別16）：

@Override 
public void onConfigure(SQLiteDatabase db) { 
    db.setForeignKeyConstraintsEnabled(true); 
}

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2013-12-14 08:15:51

Спасибозаdb.setForeignKeyConstraintsEnabled（true）; !!! –

Android的SQLite外鍵不工作

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