text: SELECT
     artist,
     week,
     streams_millions,
     streams_millions - LAG(streams_millions, 1, streams_millions) OVER ( 
        PARTITION BY artist
        ORDER BY week 
     ) AS 'streams_millions_change',
     chart_position,
     LAG(chart_position, 1, chart_position) OVER ( 
        PARTITION BY artist
        ORDER BY week 
  ) - chart_position AS 'chart_position_change'
  FROM
     streams
  WHERE 
     artist = 'Lady Gaga';