SELECT ROUND(SUM(TOTAL_VALUE) / 2,0) SA_MEDIAN
FROM (
   SELECT
      TOTAL_VALUE
   FROM
      (
         SELECT
            *
         FROM
            CONVENIENCE
         WHERE
            SURVEY_YEAR = 2019
            AND KIND_CODE = '100'
         ORDER BY
            TOTAL_VALUE
      )
   LIMIT 2 OFFSET 18
)