SQLiteDatabase只有在不存在的情況下才會添加

Question

我正在執行「添加到收藏夾」功能。用戶應該能夠將數據添加到數據庫的位置。

DatabaseHandler正在工作，我創建了一個類來處理get/set方法。

我可以很容易地將數據添加到數據庫，但我不能完全弄清楚如何檢查特定的ID是否已經存在，從而不會將重複數據添加到數據庫。

這裏是我的數據庫處理器：

public class DatabaseHandler extends SQLiteOpenHelper { 

// All Static variables 
// Database Version 
private static final int DATABASE_VERSION = 1; 

// Database Name 
private static final String DATABASE_NAME = "favoriteMovies"; 

// DataFavorites table name 
private static final String TABLE_NAME = "movies"; 

// DataFavorites Table Columns names 
private static final String KEY_ID = "id"; 
private static final String KEY_TITLE = "title"; 
private static final String KEY_URL = "url"; 
private static final String KEY_RELEASEDATE = "releaseDate"; 


public DatabaseHandler(Context context) { 
    super(context, DATABASE_NAME, null, DATABASE_VERSION); 
} 

// Creating Tables 
@Override 
public void onCreate(SQLiteDatabase db) { 

    String CREATE_DATAFAVORITES_TABLE = "CREATE TABLE " + TABLE_NAME + "(" 
      + KEY_ID + " INTEGER PRIMARY KEY," + KEY_TITLE + " TEXT," 
      + KEY_URL + " TEXT,"+ KEY_RELEASEDATE + " TEXT" + ")"; 
    db.execSQL(CREATE_DATAFAVORITES_TABLE); 



} 

// Upgrading database 
@Override 
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { 

    // Drop older table if existed 
    db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME); 

    // Create tables again 
    onCreate(db); 

} 


// Adding new movie 
public void addMovie(DataFavorites movie) { 

    SQLiteDatabase db = this.getWritableDatabase(); 

    ContentValues values = new ContentValues(); 
    values.put(KEY_ID, movie.getId()); // movie id 
    values.put(KEY_TITLE, movie.getTitle()); // movie title 
    values.put(KEY_URL, movie.getUrl()); // movie url (poster) 
    values.put(KEY_RELEASEDATE, movie.getReleaseDate()); // movie url (poster) 

    // Inserting Row 
    db.insert(TABLE_NAME, null, values); 
    db.close(); // Closing database connection 

} 

// Getting single movie 
public DataFavorites getMovie(int id) { 

    SQLiteDatabase db = this.getReadableDatabase(); 

    Cursor cursor = db.query(TABLE_NAME, new String[] { KEY_ID, 
        KEY_TITLE, KEY_URL, KEY_RELEASEDATE }, KEY_ID + "=?", 
      new String[] { String.valueOf(id) }, null, null, null, null); 
    if (cursor != null) 
     cursor.moveToFirst(); 

    DataFavorites movie = new DataFavorites(Integer.parseInt(cursor.getString(0)), 
      cursor.getString(1), cursor.getString(2), cursor.getString(3)); 
    // return movie 
    return movie; 

} 

// Getting All movie 
public List<DataFavorites> getAllMovie() { 

    List<DataFavorites> movieList = new ArrayList<DataFavorites>(); 
    // Select All Query 
    String selectQuery = "SELECT * FROM " + TABLE_NAME; 

    SQLiteDatabase db = this.getWritableDatabase(); 
    Cursor cursor = db.rawQuery(selectQuery, null); 

    // looping through all rows and adding to list 
    if (cursor.moveToFirst()) { 
     do { 
      DataFavorites dataFavorites = new DataFavorites(); 

      dataFavorites.setId(Integer.parseInt(cursor.getString(0))); 
      dataFavorites.setTitle(cursor.getString(1)); 
      dataFavorites.setUrl(cursor.getString(2)); 
      dataFavorites.setReleaseDate(cursor.getString(3)); 

      // Adding movie to list 
      movieList.add(dataFavorites); 
     } while (cursor.moveToNext()); 
    } 

    // return movie list 
    return movieList; 

} 

// Getting movie Count 
public int getMoviesCount(){ 

    String countQuery = "SELECT * FROM " + TABLE_NAME; 
    SQLiteDatabase db = this.getReadableDatabase(); 
    Cursor cursor = db.rawQuery(countQuery, null); 
    cursor.close(); 

    // return count 
    return cursor.getCount(); 

} 

// Updating single movie 
public int updateMovie(DataFavorites movie) { 

    SQLiteDatabase db = this.getWritableDatabase(); 

    ContentValues values = new ContentValues(); 
    values.put(KEY_ID, movie.getId()); 
    values.put(KEY_TITLE, movie.getTitle()); 
    values.put(KEY_URL, movie.getUrl()); 
    values.put(KEY_RELEASEDATE, movie.getReleaseDate()); 

    // updating row 
    return db.update(TABLE_NAME, values, KEY_ID + " = ?", 
      new String[] { String.valueOf(movie.getId()) }); 

} 

// Deleting single movie 
public void deleteMovie(DataFavorites movie) { 

    SQLiteDatabase db = this.getWritableDatabase(); 
    db.delete(TABLE_NAME, KEY_ID + " = ?", 
      new String[] { String.valueOf(movie.getId()) }); 
    db.close(); 

} 

在這裏，我想補充的數據，如果ID不存在：

public void AddToFavorites(MenuItem item) { 

    DatabaseHandler db = new DatabaseHandler(this); 

    /* if (id is not there){ 

    // Inserting movie 
    Log.d("Insert: ", "Inserting movie.."); 
    db.addMovie(new DataFavorites(Integer.parseInt(Id), Title, Poster, Release)); 
} */ 

} 

Answer 1

添加UNIQUE索引表列，以防止重複的條目。另外請注意，它會拋出一個異常，如果重複插入，所以不要忘記來處理

Answer 2

你應該使用：

db.execSql("INSERT OR IGNORE INTO movies (columns names) VALUES (your values)"); 

或

db.execSql("INSERT OR REPLACE INTO movies (columns names) VALUES (your values)"); 

插入值，如果他們已經在表格中，他們不會被添加（第一種方法），或者他們將被替換（第二種方法）。