mysql获取近7天日期

SELECT
      date_sub( curdate( ), INTERVAL 7 DAY ) AS a UNION
      SELECT
      date_sub( curdate( ), INTERVAL 6 DAY ) AS a UNION
      SELECT
      date_sub( curdate( ), INTERVAL 5 DAY ) AS a UNION
      SELECT
      date_sub( curdate( ), INTERVAL 4 DAY ) AS a UNION
      SELECT
      date_sub( curdate( ), INTERVAL 3 DAY ) AS a UNION
      SELECT
      date_sub( curdate( ), INTERVAL 2 DAY ) AS a UNION
      SELECT
      date_sub( curdate( ), INTERVAL 1 DAY ) AS a
      FROM DUAL

 往前推几天或者几年