BigQuery 日期和时间函数在时间戳列上返回 NULL

Question

我正在使用 LAG() 和 LEAD() 从 table 中的一个时间戳列中提取 3 个时间戳列：时间戳、prev_timestamp、next_timestamp。我需要做一些简单的日期和时间格式化，但是当我在 prev_timestamp 或 next_timestamp 上使用像 MONTH() 这样的函数时，它 returns NULL.

结果列的架构类型是正确的 (TIMESTAMP)，并且出于某种原因，常规时间戳日期和时间格式有效。我该如何做到 returns 所有 3 列的月份都正确？

returns 时间戳列的月份和上一个和下一个时间戳列的 NULL 的示例代码：

SELECT 
  MONTH(timestamp) AS month,
  MONTH(prev_timestamp) AS prev_month,
  MONTH(next_timestamp) AS next_month
FROM (
  SELECT
    timestamp,
    LAG(timestamp,1) OVER (PARTITION BY id ORDER BY timestamp) prev_timestamp,
    LEAD(timestamp,1) OVER (PARTITION BY id ORDER BY timestamp) next_timestamp
  FROM timestamp_table
  )

Answer 1

试试下面

SELECT 
  MONTH(MSEC_TO_TIMESTAMP(timestamp)) AS month,
  MONTH(MSEC_TO_TIMESTAMP(prev_timestamp)) AS prev_month,
  MONTH(MSEC_TO_TIMESTAMP(next_timestamp)) AS next_month
FROM (
  SELECT
    timestamp,
    LAG(timestamp,1) OVER (PARTITION BY id ORDER BY timestamp) prev_timestamp,
    LEAD(timestamp,1) OVER (PARTITION BY id ORDER BY timestamp) next_timestamp
  FROM timestamp_table
  )

Answer 2

所以在测试和检查了几件事之后，我实际上从中启发了自己并意识到他的答案是不正确的，因为 lag/lead 没有 return 毫秒，但是微秒（为什么？这是任何人的猜测）。

SELECT 
  MONTH(timestamp) AS month,
  MONTH(MSEC_TO_TIMESTAMP((prev_timestamp/1000))) AS prev_month,
  MONTH(MSEC_TO_TIMESTAMP((next_timestamp/1000))) AS next_month
FROM (
  SELECT
    timestamp,
    LAG(timestamp,1) OVER (PARTITION BY id ORDER BY timestamp) prev_timestamp,
    LEAD(timestamp,1) OVER (PARTITION BY id ORDER BY timestamp) next_timestamp
  FROM timestamp_table
  )

应该可以。我刚刚测试了创建一个包含三行时间戳的 table。在没有 /1000 的情况下使用它，我的 lagged/lead 版本给出了不同的月份。我测试了结果，如果你不做除法，你最终会在第 47 个千年的某个地方。

BigQuery 日期和时间函数在时间戳列上返回 NULL

BigQuery Date and Time Functions returning NULL on a timestamp column

google-bigquery