Question

我有一个timestamp列，用于跟踪外部传感器何时记录读数。此列转到microsecond，但我想将数据截断为decisecond以进行分组。

此truncate function效果很好，但只允许解析millisecond或microsecond。我只需要将我的数据修剪为decisecond以解决我的收集过程中的错误。

有没有办法将timestamp列修剪为decisecond？

Answer 1

将Now()（当前时间）替换为您选择的列：

select 
  -- current time
  now(), 

  -- current time truncated to minutes
  date_trunc('minute', Now()), 

  -- seconds from timestamp, including decimal part
  extract(seconds from Now()),

  -- seconds truncated to first decimal digit (results in seconds and decisecond)
  trunc((extract(seconds from Now()))::numeric, 1),

  -- add time truncated to minutes and seconds truncated to first decimal digit
  date_trunc('minute', Now()) 
     + interval '1 second' * trunc((extract(seconds from Now()))::numeric, 1)

请注意，由于numeric返回extract()而double precision仅接受trunc(x, y)（请参阅documentation）numeric >

对于名为mytime的列，这将是：

  date_trunc('minute', mytime) 
     + interval '1 second' * trunc((extract(seconds from mytime))::numeric, 1)

另一种选择是截断epoch：

select 
  -- current time
  now(), 

  -- epoch - number of seconds since epoch beginning, including decimal part
  extract(epoch from Now()),

  -- truncated to first decimal digit
  trunc((extract(epoch from Now()))::numeric, 1),

  -- converted back to timestamp
  to_timestamp(trunc((extract(epoch from Now()))::numeric, 1))

对于名为mytime的列，这将是：

  to_timestamp(trunc((extract(epoch from mytime))::numeric, 1))

文档：extract，epoch，to_timestamp

Postgres截断时间戳截断到Decisecond

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