Question

我正在尝试创建一个如下表：

| year | week_number | first_week_day | last_week_day |
-------------------------------------------------------
| 2019 |     1       |   2019-01-01   | 2019-01-07    |
.......................................................

我已经搜索了实现方法，并决定使用EXTRACT和GENERATE_DATE。如果有更好的方法，请告诉我。

这是我到目前为止所拥有的：

#StandardSQL
WITH

  dates_2018 AS
(SELECT GENERATE_DATE_ARRAY("2018-01-01", "2018-12-31") AS d_2018)

 ,dates_2019 AS
(SELECT GENERATE_DATE_ARRAY("2019-01-01", "2019-12-31") AS d_2019)


SELECT un

FROM dates_2018, UNNEST(d_2018) AS un
--  ,timestamps_2018 AS
-- (SELECT TIMESTAMP(dates_2018) AS timestamps_2018
-- FROM UNNEST(dates_2018))

--  ,d_2018 AS
-- (SELECT EXTRACT(year from timestamps_2018) AS year
--       ,EXTRACT(week from timestamps_2018) AS week
--       ,EXTRACT(day from timestamps_2018) AS day
-- FROM timestamps_2018)

-- SELECT *

-- FROM timestamps_2018

我现在的问题在于我无法纠正UNNEST数组d_2018的事实，因此我可以将所有元素转换为时间戳，以便以后可以从中提取内容。

当我取消嵌套时，它仅返回第一行。

主要是我正在寻找这个毫不费力的修复程序，但是如果有人可以提供更多建议，那么它将受到欢迎。

Answer 1

我不确定您为什么将每年的数据分开。根据您的描述：

WITH dates AS (
      SELECT GENERATE_DATE_ARRAY('2018-01-01', '2019-12-31') as date_array
     )
select extract(year from d) as year, d,
       EXTRACT(week from d) as week,
       date_trunc(d, week) as first_week_day,
       date_add(date_trunc(d, week), interval 6 day) as last_week_day
from dates cross join
     unnest(date_array) d
ORDER BY d;

Answer 2

UNNEST将数组条目转换为表行，以便您可以在它们上运行SQL。我不确定您要做什么，但是您完全可以做类似的事情

SELECT 
 d,
 extract(WEEK from d) CW,
 extract(DAY from d) day,
 extract(YEAR from d) year
FROM UNNEST(GENERATE_DATE_ARRAY("2018-01-01", "2019-12-31")) AS d

将generate_date_array()中的数组输入unnest()

Answer 3

以下是用于BigQuery标准SQL

#standardSQL
SELECT DISTINCT
  EXTRACT(YEAR FROM day) AS year,
  EXTRACT(WEEK FROM day) + 1 AS week_number,
  DATE_TRUNC(day, WEEK) AS first_week_day,
  DATE_ADD(DATE_TRUNC(day, week), INTERVAL 6 DAY) AS last_week_day
FROM UNNEST(GENERATE_DATE_ARRAY('2018-01-01', '2019-12-31')) AS day

如何在Big Query中正确取消嵌套此数组？

3 个答案: