when do we change the database version number in android

when do we have to change the database version number, 1)if i am adding new table 2)if i am adding new fields to an existing table. also does the change in database version affect the way i am accessing data from other tables. What is the correct way to change the database version. `

public MyDBHelper(Context context, String name, CursorFactory factory, int version) { super(context, name, factory, 1);

}

`(please mention if there are other cases where we have to change the database version). Thanks in advance.