从 Bigquery 中的时间戳中提取日期：一种更可取的方法

Question

向 Bigquery 专家提问。

这是使用标准 SQL 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 的论点是，如果您在选择列表中提取其他日期/时间部分，它会反映它们。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;

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;