如何计算日期维度的iso_week_start_date和iso_week_end_date？

Question

作为日历维度的一部分，我需要填充iso_week_start_date，iso_week_end_date和iso_week_number。除了这些字段，我已经能够构建日历维度。谢谢。

Answer 1

Snowflake提供DATE_TRUNC(WEEK, ..)它可以让你获得ISO周的第一天。然后添加6天给你最后一天。还有还有DATE_EXTRACT(WEEK, ..)（或简称WEEK(..)）

例如：

select extract(week, '2017-10-10'::date), date_trunc(week, '2017-10-10'::date), dateadd(day, 6, date_trunc(week, '2017-10-10'::date)); 
-----------------------------------+--------------------------------------+-------------------------------------------------------+ 
EXTRACT(WEEK, '2017-10-10'::DATE) | DATE_TRUNC(WEEK, '2017-10-10'::DATE) | DATEADD(DAY, 6, DATE_TRUNC(WEEK, '2017-10-10'::DATE)) | 
-----------------------------------+--------------------------------------+-------------------------------------------------------+ 
41        | 2017-10-09       | 2017-10-15           | 
-----------------------------------+--------------------------------------+-------------------------------------------------------+ 

记住，ISO周有一个有点怪异的语义，请参阅文档以了解详情。