我有这样的SQL查询

String loadFav = "SELECT _id, title, name, favorite FROM table1 where favorite= 1 " 
                     + "UNION ALL" 
                     + "SELECT _id, title, name, favorite FROM table2 where favorite= 1"
                     ;

    Cursor mCursor = mSQLiteDatabase.rawQuery(loadFav, null);

运行此查询时出现错误。结构正确吗？有人能帮我吗？