使用OrmLiteSqliteOpenHelper类安装在Sqlite数据库的alter table中的问题

Question

朋友们，我想通过下面的程序在我的应用程序中添加新列是我的代码

public class DatabaseConnectionAPI extends OrmLiteSqliteOpenHelper {
public DatabaseConnectionAPI(Context context) {

        super(context, DB_PATH + DB_NAME, null, 1);
        this.myContext = context;


    }


    public    void openDataBase() throws SQLException {
    try {
        db.close();
    } catch (Exception e) {
        System.out.println("no database connected to close");
    }
    // Open the database
    String myPath = DB_PATH + DB_NAME;
    db = SQLiteDatabase.openDatabase(myPath, null,
            SQLiteDatabase.OPEN_READWRITE);
    onUpgrade(db, connectionSource, 1, 2);

    System.out.println("Databse opened...." + db);
}

@Override
public synchronized void close() {
    if (db != null)
        db.close();

    super.close();
}

    @Override
    public void onCreate(SQLiteDatabase arg0, ConnectionSource arg1) {

        System.out.println("Create DB");

        try {
            TableUtils.createTable(connectionSource, Property_Master.class);
         } catch (SQLException e) {
            Log.e(DatabaseConnectionAPI.class.getName(), "Can't create database", e);
            throw new RuntimeException(e);
        } catch (java.sql.SQLException e) {
            e.printStackTrace();
        }

    }

    @Override
    public void onUpgrade(SQLiteDatabase arg0, ConnectionSource arg1, int arg2,
            int arg3) {


        try {
            ArrayList<String> allSql = new ArrayList<String>(); 
            switch(arg2) 
            {
              case 1: 
                  allSql.add("ALTER TABLE " + "property_master" + " ADD COLUMN " + " p_type " + "VARCHAR");
             }
            for (String sql : allSql) {
                db.execSQL(sql);
            }
        } catch (SQLException e) {
            Log.e(DatabaseConnectionAPI.class.getName(), "exception during onUpgrade", e);
            throw new RuntimeException(e);
        }

    }

}

在上面的代码上运行时，它给我错误，如下所示

 android.database.sqlite.SQLiteException: duplicate column name: p_type: ALTER TABLE property_master ADD COLUMN  p_type VARCHAR

任何想法我该如何解决？