#standardSQL
CREATE TEMPORARY FUNCTION lab_TIME(x ARRAY<TIMESTAMP>)
  RETURNS INT64
  LANGUAGE js AS """
  var total_time = 0;
  //loop through
  for (var i = 0; i < x.length -1; i+=2)
  { total_time += x[i+1] - x[i]; }
  return total_time/1000;
""";
SELECT
  lab_member AS user,
  lab_TIME(access_timestamps) AS total_lab_time
FROM (
  SELECT
    Name AS lab_member,
    ARRAY_AGG(LabAccessTS) AS access_timestamps
  FROM (
    SELECT
      Name,
      LabAccessTS
    FROM
      `secret_lab.door_scans_20140214`
    GROUP BY
      Name,
      LabAccessTS
    ORDER BY
      Name,
      LabAccessTS ASC)
 GROUP BY
   lab_member);