Working with a database in Android

/**
 * Database Wrapper
 *
 * DB Schema:
 * ------------------------------------
 * Create table tblData (
 *     _id int primary key autoincrement,
 *     alert_text text,
 *     alert_date varchar(20),
 *     alert_time varchar(20)
 * );
 */
public class DBLayer {

	/*******************************************************
	* These constants refer to the fields in the database.
	* _id is Android's naming convention for ID fields.
	* Our database has 3 fields, so we have 3 constants.
	********************************************************/

	public static final String KEY_NAME  = "name";
	public static final String KEY_VAL   = "value";
	public static final String KEY_ROWID = "_id";

	/*******************************************************
	* This is not needed for the database. It is
	* here to help us tag our logging messages
	*******************************************************/
	public static final String TAG = "AlertDB";

	private DatabaseHelper dbHelper ;
	private SQLiteDatabase db;

	private Context mCtx = null;

	/*******************************************************
	* Some other constants related to our database's
	* information. They should be self explanatory
	********************************************************/
	private static final String DATABASE_NAME = "gAlert_db";
	private static final String DATABASE_TABLE = "tblData";
	private static final int DATABASE_VERSION = 2;
	private static final String DATABASE_CREATE =
	"create table gAlert_alerts ( "
	+ "_id integer primary key autoincrement, "
	+ "alert_text text not null,"
	+ "alert_date varchar(20) not null,"
	+ "alert_time varchar(20) not null"
	+");";

	/********************************************************
	* Think of this as a driver for your database
	* interaction. You can just copy and paste this part in
	* all your database interaction classes.
	*********************************************************/
	private static class DatabaseHelper extends SQLiteOpenHelper {
		DatabaseHelper(Context ctx) {
			super(ctx, DATABASE_NAME, null, DATABASE_VERSION);
		}
		@Override
		public void onCreate(SQLiteDatabase db) {
			db.execSQL(DATABASE_CREATE);
		}
		@Override
		public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
			db.execSQL("DROP IF TABLE EXISTS "+DATABASE_TABLE);
			onCreate(db);
		}
	}

	/** Constructor */
	public DBLayer(Context ctx) {
		mCtx = ctx;
	}
	/********************************************************
	* This opens a connection to the database but if
	* something goes wrong, it will throw an exception.
	********************************************************/
	public DBLayer open () throws SQLException {
		dbHelper = new DatabaseHelper(mCtx);
		db = dbHelper.getWritableDatabase();
		return this;
	}
	/** Closes a database connection */
	public void close() {
		dbHelper.close();
	}
}

	public Cursor fetchAllAlerts() {
		try {
			return db.query(DATABASE_TABLE,
				new String[] {KEY_ALERT_TEXT, KEY_ALERT_DATE,
				KEY_ALERT_TIME, KEY_ROWID}, null, null,
				null, null, null);
		} catch (Exception e) {
			Log.e("yo", e.getMessage());
			return null;
		}
	}

	public long createAlert(String text, String date, String time) {
	ContentValues vals = new ContentValues();
	vals.put(KEY_ALERT_TEXT, text);
	vals.put(KEY_ALERT_DATE, date);
	vals.put(KEY_ALERT_TIME, time);
	return db.insert(DATABASE_TABLE, null, vals);
}

public boolean deleteAlert(long rowId) {
	return db.delete(DATABASE_TABLE, KEY_ROWID+"="+rowId, null) > 0;
}

public Cursor fetchAllAlerts() {
	try {
		return db.query(DATABASE_TABLE, new String[] {
				KEY_ALERT_TEXT, KEY_ALERT_DATE,
				KEY_ALERT_TIME, KEY_ROWID}, 
					null, null, null, null, null);
	} catch (Exception e) {
		Log.e("yo", e.getMessage());
		return null;
	}
}

public Cursor fetchAlert(long rowId) throws SQLException {
	Cursor ret = db.query(DATABASE_TABLE, new String[] {
				KEY_ALERT_TEXT, KEY_ALERT_DATE,
				KEY_ALERT_TIME, KEY_ROWID},
				KEY_ROWID+"="+rowId, null, null,
				null, null);
	if (ret != null) {
		ret.moveToFirst();
	}
	return ret;
}

public boolean updateAlert(long rowId, String text, String date, String time) {
	ContentValues vals = new ContentValues();
	vals.put(KEY_ALERT_TEXT, text);
	vals.put(KEY_ALERT_DATE, date);
	vals.put(KEY_ALERT_TIME, time);
	return db.update(DATABASE_TABLE, vals,KEY_ROWID+"="+rowId, null) > 0;
}