Question

我有一张包含这些信息的表：

July 16th 2018, 11:16:35.408    July 16th 2018, 11:16:35.408    appointmentCard flip    event       5afa7e01-6045-4ff5-b2d7-1933cd16ebca
July 16th 2018, 11:16:18.649    July 16th 2018, 11:16:18.649    5afa7e01-6045-4ff5-b2d7-1933cd16ebca

我需要在两个不同的列中提取日期和小时。我尝试过：

select
    to_char(mlk.time, 'yyyy-mm-dd') as Date,
    to_char(mlk.time, 'HH24:MI') as Hours
from main_source_multichannel mlk 
    inner join main_source_orders ord on mlk.trackingid = ord.trackingid

没有成功，Postgresql给我这个错误：

SQL Error [42883]: ERROR: function to_char(character varying) does not exist
  Hint: No function matches the given name and argument types. You might need to add explicit type casts.
  Position: 10
  ERROR: function to_char(character varying) does not exist
  Hint: No function matches the given name and argument types. You might need to add explicit type casts.
  Position: 10
  ERROR: function to_char(character varying) does not exist
  Hint: No function matches the given name and argument types. You might need to add explicit type casts.
  Position: 10

我做错了什么？谢谢

Answer 1

日期的格式使其比所需的要复杂一些。我将使用子查询将其解析为时间戳，然后提取日期和时间就变得很简单。这是如何执行此操作的示例：SQL Fiddle

在您的情况下，类似：

WITH dates AS (
  SELECT to_timestamp(mlk.time, 'MonBDDBBBYYYYBBHH:MI:SS:MS') AS dateTime
  FROM main_source_multichannel mlk 
  INNER JOIN main_source_orders ord on mlk.trackingid = ord.trackingid
)
SELECT dateTime::date AS theDate, dateTime::time AS theTime
FROM dates

正如其他答案所建议的那样，将数据存储为适当的时间戳将消除子查询的需要，而您只需要一个简单的SELECT。

Answer 2

我可能会在您的SELECT中尝试以下操作。

SELECT
to_char((mlk.time)::TIMESTAMP) , 'yyyy-mm-dd')    AS date
,to_char((mlk.time)::TIMESTAMP), 'HH24:MI')       AS hours

如果可以的话，我也会尝试将数据存储为TIMESTAMP 如果无法将列强制转换为::TIMESTAMP，则可能需要修复这些记录。

从varchar中提取日期

2 个答案: