在考虑时区的同时获取PostgreSQL中日期的记录数

Question

鉴于我在postgresql中有一个带有created_at列的checkins表,我如何在考虑时区的同时选择在给定日期(例如2012-10-17)创建的所有记录'America/New_York'(并考虑到夏令时)？

目前我正在执行以下查询,psql (PostgreSQL) 9.1.6但似乎缺少一些在当天结束时添加的记录.

SELECT COUNT(*) AS count FROM checkins WHERE date(created_at) = '2012-10-17';

这是给定日期的所有记录的列表.上面的查询返回10,这是不正确的.我应该回来13.

  id  | waiver_id |         created_at         |         updated_at         
------+-----------+----------------------------+----------------------------
 1391 |         1 | 2012-10-18 00:42:07.308453 | 2012-10-18 00:42:07.308453
 1390 |       286 | 2012-10-18 00:38:53.102685 | 2012-10-18 00:38:53.102685
 1389 |       590 | 2012-10-18 00:38:28.811605 | 2012-10-18 00:38:28.811605
 1388 |         7 | 2012-10-17 22:29:25.610774 | 2012-10-17 22:29:25.610774
 1387 |      1155 | 2012-10-17 22:01:40.647219 | 2012-10-17 22:01:40.647219
 1386 |      1154 | 2012-10-17 22:00:05.477698 | 2012-10-17 22:00:05.477698
 1385 |      1153 | 2012-10-17 21:57:59.698076 | 2012-10-17 21:57:59.698076
 1384 |      1152 | 2012-10-17 21:08:32.533203 | 2012-10-17 21:08:32.533203
 1383 |      1151 | 2012-10-17 21:07:42.500036 | 2012-10-17 21:07:42.500036
 1382 |       115 | 2012-10-17 21:04:03.075333 | 2012-10-17 21:04:03.075333
 1381 |         3 | 2012-10-17 20:30:13.741647 | 2012-10-17 20:30:13.741647
 1380 |       245 | 2012-10-17 20:29:53.808852 | 2012-10-17 20:29:53.808852
 1379 |      1150 | 2012-10-17 20:27:30.057269 | 2012-10-17 20:27:30.057269

checkins columns&data_types

 column_name |          data_type          
-------------+-----------------------------
 updated_at  | timestamp without time zone
 created_at  | timestamp without time zone
 waiver_id   | integer
 id          | integer

Answer 1

根据您的具体需求,AT TIME ZONE构造可以提供帮助.

如果您的列属于类型timestamp [without time zone]且您的本地时间设置为与EST不同的时区,但您希望EST的相应日期,则这将是您的查询:

SELECT count(*) AS ct
FROM   checkins
WHERE  (created_at AT TIME ZONE 'EST')::date = '2012-10-16';

不能肯定地说,你的问题是缺少基本信息,并留有解释空间.
在这个相关的答案中,通过示例和链接全面解释PostgreSQL的时区处理.

如果要自动覆盖夏令时,请使用时区名称而不是时区缩写.喜欢:

created_at AT TIME ZONE 'America/New_York'

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