我想在第一个“添加到购物车”事件之前计算“产品视图”事件的数量。
可以使用窗口函数计算此值：

SELECT userId, seqnum - 1
FROM (SELECT t.*, hits,
             ROW_NUMBER() OVER (PARTITION BY ut.userId ORDER BY h.time) as seqnum,
             ROW_NUMBER() OVER (PARTITION BY ut.userId, eventAction ORDER BY h.time) as seqnum_ea
      FROM `table_name` t CROSS JOIN
           UNNEST(t.hits) AS hits
      WHERE hits.eventInfo.eventCategory IS NOT NULL AND
            hits.eventInfo.eventCategory = 'Ecommerce' AND
            hits.eventInfo.eventAction IN ('Product View', 'Add to Cart')
     ) t
WHERE hits.eventInfo.eventAction = 'Add to Cart' AND seqnum_ea = 1;