如何在没有SQLiteOpenHelper的情况下在app中升级SQLite表

public  static SQLiteDatabase attendancedb = this.openOrCreateDatabase("Attendance", Context.MODE_PRIVATE, null);

attendancedb.execSQL("CREATE TABLE IF NOT EXISTS attendance ( subName VARCHAR , attend VARCHAR, total VARCHAR, PRIMARY KEY (subName))");

如何在表中再添加一列(注释)?

attendancedb.execSQL("CREATE TABLE IF NOT EXISTS attendance ( subName VARCHAR , attend VARCHAR, total VARCHAR,notes VARCHAR, PRIMARY KEY (subName))");

更新的应用程序在访问notes数据时崩溃,

不 SQLiteOpenHelper 班

这是解决方案

public class DatabaseHelper extends SQLiteOpenHelper {

public DatabaseHelper(Context context) {

    super(context, "Attendance", null, 1);

}

@Override
public void onCreate(SQLiteDatabase sqLiteDatabase) {

    if(checktable(sqLiteDatabase)==0){ //for old user
        try {
            sqLiteDatabase.execSQL("ALTER TABLE attendance ADD notes VARCHAR;");
        }catch (Exception e){  //for new user

            sqLiteDatabase.execSQL("CREATE TABLE  attendance ( subName VARCHAR , attend VARCHAR, total VARCHAR,notes VARCHAR, PRIMARY KEY (subName))");
        }
    }
    }

@Override
public void onUpgrade(SQLiteDatabase sqLiteDatabase, int old, int newVersion) {


}



int checktable(SQLiteDatabase db){

    try{
    Cursor c= db.rawQuery("SELECT notes FROM  attendance", null);


        return 1;
    }catch (Exception e){

        return 0;
    }

    }
  }