從Bigquery中的時間戳提取日期：一種更好的方法

Question

Bigquery大師的一個簡單問題。

這裏有兩種方法使用standardSQL

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

BigQuery中的時間戳提取日期哪一個更理想，爲什麼？謝謝！

Answer 1

這真的歸結爲個人喜好;由於它們具有相同的語義和性能，因此一個並不優於另一個。支持使用EXTRACT的觀點是，如果您在選擇列表中提取其他日期/時間部分，則會反映它們。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;