不断收到“无法访问类型为 ARRAY<STRUCT<hitNumber INT64, time INT64, hour INT64, ...>> 的值的字段项”答案

【问题标题】：Keep getting "Cannot access field item on a value with type ARRAY<STRUCT<hitNumber INT64, time INT64, hour INT64, ...>>"不断收到“无法访问类型为 ARRAY<STRUCT<hitNumber INT64, time INT64, hour INT64, ...>> 的值的字段项”
【发布时间】：2021-03-11 07:26:05
【问题描述】：

我正在复制并粘贴 Google Analytics Cookbook 中的代码：

SELECT one.hits.item.productSku AS ProductSku, ( sum_of_hit_number / total_hits ) AS avg_hit_number
FROM (
 SELECT hits.item.productSku, SUM(hits.hitNumber) AS sum_of_hit_number
 FROM [‘GA Dataset Name’ ]
 WHERE hits.item.productSku IS NOT NULL
  AND totals.transactions>=1
 GROUP BY hits.item.productSku ) AS ‘Alias_Name_1’
JOIN (
 SELECT hits.item.productSku, COUNT( fullVisitorId ) AS total_hits
 FROM [‘GA Dataset Name’ ]
 WHERE hits.item.productSku IS NOT NULL
  AND totals.transactions>=1
 GROUP BY hits.item.productSku ) AS ‘Alias_Name_2’
ON Alias_Name_1.hits.item.productSku = Alias_Name_2.hits.item.productSku;

但我将其编辑为：

SELECT one.hits.item.productSku AS ProductSku, ( sum_of_hit_number / total_hits ) AS avg_hit_number
FROM (
 SELECT hits.item.productSku, SUM(hits.hitNumber) AS sum_of_hit_number
 FROM `bigquery-public-data.google_analytics_sample.ga_sessions_20170801`
 WHERE hits.item.productSku IS NOT NULL
  AND totals.transactions>=1
 GROUP BY hits.item.productSku ) AS ProductSKU_Item
JOIN (
 SELECT hits.item.productSku, COUNT( fullVisitorId ) AS total_hits
 FROM `bigquery-public-data.google_analytics_sample.ga_sessions_20170801`
 WHERE hits.item.productSku IS NOT NULL
  AND totals.transactions>=1
 GROUP BY hits.item.productSku ) AS product2_item
ON ProductSKU_Item.hits.item.productSku = product2_item.hits.item.productSku;

我仍然收到一条错误消息，提示 Cannot access field item on a value on type ARRAY> at [5:13] 但是当我尝试 UNNEST 功能时，它仍然无法正常工作，我不确定自己做错了什么。

【问题讨论】：

标签： sql standards

【解决方案1】：

我使用unnest 犯的错误是尝试取消嵌套hits.item，即struct。 hits 是需要unnested 的数组。试试这个：

SELECT
  hits.item.productSku,
  SUM(hits.hitNumber) / COUNT( fullVisitorId ) AS avg_hit_number
FROM
  `bigquery-public-data.google_analytics_sample.ga_sessions_20170801` t
CROSS JOIN
  UNNEST(t.hits) AS hits
WHERE
  hits.item.productSku IS NOT NULL
  AND totals.transactions >= 1
GROUP BY
  hits.item.productSku

【讨论】：