SELECT
  MIN(TD_TIME_FORMAT(time,'yyyy-MM-dd','JST')) AS min_d,
  MAX(TD_TIME_FORMAT(time,'yyyy-MM-dd','JST')) AS max_d
FROM access_log
/* TD_SCHEDULED_TIME の日付(2017-08-08)を含む過去7日間 */
WHERE TD_TIME_RANGE(
  time,
  TD_DATE_TRUNC('day',TD_TIME_ADD(TD_SCHEDULED_TIME(),'-6d','JST'),'JST'),
  TD_DATE_TRUNC('day',TD_TIME_ADD(TD_SCHEDULED_TIME(),'1d','JST'),'JST'),
  'JST'
)