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Question

我正在尝试获取客户的第一个订单，下一个订单以及两个订单之间的天数差异。看起来很简单。我遵循的步骤如下：

使用MIN（）和LEAD（）函数
使用这两个字段运行DATEDIFF以获得天数差异。

简要说明如下：

SELECT cust, MIN(ord_time) first_ord, LEAD(ord_time, 1) 
                                      OVER 
                                      (PARTITION BY customer_id
                                      ORDER BY ord_time) next_ord
FROM
(SELECT cust, ord_time
FROM df.orders
GROUP EACH BY cust, ord_time)

其中还有一些其他过滤连接和分组，但这是基本块。

输出应该是包含客户ID的字段和两个时间戳字段。两个时间戳字段如下所示：

Timestamps in Output

所以一切看起来都很棒。但是，当我尝试用两个字段运行DATEDIFF（）函数时，一切都回来了。

此外，当我将鼠标悬停在任一时间戳字段上时，它告诉我数据类型是TIMESTAMP，但是当我尝试将任何类型的时间戳转换运行到秒或其他任何时候，next_ord字段导致它失败，错误为“类型未知“。

只是寻找任何我做错的事情或以任何方式解决这个问题。

感谢您的帮助。

Answer 1

我认为这与wondow函数如何处理时间戳

有关

这是我到目前为止看到的：

1

当源数据点是字符串时 - 全部用作预期：

SELECT 
  customer_id,
  first_ord,
  next_ord,
  DATEDIFF(next_ord, first_ord) AS diff
FROM (
  SELECT 
    customer_id, 
    LEAD(ord_time, 0) OVER (PARTITION BY customer_id ORDER BY ord_time) first_ord, 
    LEAD(ord_time, 1) OVER (PARTITION BY customer_id ORDER BY ord_time) next_ord,
    ROW_NUMBER() OVER (PARTITION BY customer_id ORDER BY ord_time) num
  FROM 
    (SELECT 1 AS customer_id, '2014-04-08 09:51:24 UTC' AS ord_time),
    (SELECT 1 AS customer_id, '2014-04-08 09:53:31 UTC' AS ord_time),
    (SELECT 1 AS customer_id, '2014-05-08 09:53:31 UTC' AS ord_time),
    (SELECT 2 AS customer_id, '2014-09-12 17:20:43 UTC' AS ord_time),
    (SELECT 2 AS customer_id, '2015-04-16 21:44:18 UTC' AS ord_time),
)
WHERE num = 1

结果：

customer_id       first_ord             next_ord    diff     
1   2014-04-08 09:51:24 UTC 2014-04-08 09:53:31 UTC 0    
2   2014-09-12 17:20:43 UTC 2015-04-16 21:44:18 UTC 216

2

当源数据点是时间戳时 - 结果是 null ，如您在问题中所述：

SELECT 
  customer_id,
  first_ord,
  next_ord,
  DATEDIFF(next_ord, first_ord) AS diff
FROM (
  SELECT 
    customer_id, 
    LEAD(ord_time, 0) OVER (PARTITION BY customer_id ORDER BY ord_time) first_ord, 
    LEAD(ord_time, 1) OVER (PARTITION BY customer_id ORDER BY ord_time) next_ord,
    ROW_NUMBER() OVER (PARTITION BY customer_id ORDER BY ord_time) num
  FROM 
    (SELECT 1 AS customer_id, TIMESTAMP('2014-04-08 09:51:24 UTC') AS ord_time),
    (SELECT 1 AS customer_id, TIMESTAMP('2014-04-08 09:53:31 UTC') AS ord_time),
    (SELECT 1 AS customer_id, TIMESTAMP('2014-05-08 09:53:31 UTC') AS ord_time),
    (SELECT 2 AS customer_id, TIMESTAMP('2014-09-12 17:20:43 UTC') AS ord_time),
    (SELECT 2 AS customer_id, TIMESTAMP('2015-04-16 21:44:18 UTC') AS ord_time),
)
WHERE num = 1

结果：

customer_id       first_ord             next_ord    diff     
1   2014-04-08 09:51:24 UTC 2014-04-08 09:53:31 UTC null     
2   2014-09-12 17:20:43 UTC 2015-04-16 21:44:18 UTC null

3

要“修复”，我必须按照以下方式进行投射：

SELECT 
  customer_id,
  TIMESTAMP(first_ord) as first_ord,
  TIMESTAMP(next_ord) as next_ord,
  DATEDIFF(next_ord, first_ord) AS diff
FROM (
  SELECT 
    customer_id, 
    LEAD(STRING(ord_time), 0) OVER (PARTITION BY customer_id ORDER BY ord_time) first_ord, 
    LEAD(STRING(ord_time), 1) OVER (PARTITION BY customer_id ORDER BY ord_time) next_ord,
    ROW_NUMBER() OVER (PARTITION BY customer_id ORDER BY ord_time) num
  FROM 
    (SELECT 1 AS customer_id, TIMESTAMP('2014-04-08 09:51:24 UTC') AS ord_time),
    (SELECT 1 AS customer_id, TIMESTAMP('2014-04-08 09:53:31 UTC') AS ord_time),
    (SELECT 1 AS customer_id, TIMESTAMP('2014-05-08 09:53:31 UTC') AS ord_time),
    (SELECT 2 AS customer_id, TIMESTAMP('2014-09-12 17:20:43 UTC') AS ord_time),
    (SELECT 2 AS customer_id, TIMESTAMP('2015-04-16 21:44:18 UTC') AS ord_time)
)
WHERE num = 1

结果是：

customer_id       first_ord             next_ord    diff     
1   2014-04-08 09:51:24 UTC 2014-04-08 09:53:31 UTC 0    
2   2014-09-12 17:20:43 UTC 2015-04-16 21:44:18 UTC 216

在Big Query中使用`Lead`窗口函数时遇到时间戳问题

1 个答案:

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