从Bigquery中的时间戳中提取日期：一种更好的方法

Question

向Bigquery大师提出的一个简短问题。

以下是使用standardSQL

从Bigquery中的时间戳中提取日期的两种方法

#standardSQL
#1
DATE(TIMESTAMP_MILLIS(CAST((timestamp) AS INT64)))
#2
EXTRACT(DATE FROM TIMESTAMP_MILLIS(timestamp))

哪一个更可取，为什么？谢谢！

Answer 1

这真的取决于个人喜好;一个并不优于另一个，因为它们具有相同的语义和性能。支持使用EXTRACT的论据是，如果要在选择列表中提取其他日期/时间部分，则会反映它们。例如：

SELECT
  EXTRACT(DATE FROM TIMESTAMP_MILLIS(timestamp)) AS date,
  EXTRACT(ISOYEAR FROM TIMESTAMP_MILLIS(timestamp)) AS iso_year,
  EXTRACT(ISOWEEK FROM TIMESTAMP_MILLIS(timestamp)) AS iso_week
FROM YourTable;

与：相比：

SELECT
  DATE(TIMESTAMP_MILLIS(timestamp)) AS date,
  EXTRACT(ISOYEAR FROM TIMESTAMP_MILLIS(timestamp)) AS iso_year,
  EXTRACT(ISOWEEK FROM TIMESTAMP_MILLIS(timestamp)) AS iso_week
FROM YourTable;