I am trying to extract the hour from a timestamp with a timezone. However, my times are coming up incorrectly.
Here's an example, I am using Dbeaver with my timezone set to EST:
SELECT '2020-01-24 14:27:12' AT TIME ZONE 'US/Pacific' as foo,
EXTRACT(HOUR FROM foo) as ex,
DATE_PART('HOUR', foo::timestamp) as dp
RETURNS:
foo |ex |dp
2020-01-24 17:27:12 |22 | 22
Why is my time coming up 3 hours ahead, it should be 3 hours behind?
Extract and DATE_PART don't seem to get me the hour I would like. It looks like it's taking 17 as EST and then converting it to UTC. Here's what I am expecting to get:
foo |ex |dp
2020-01-24 11:27:12 |11 | 11
Check if your timezone is set to EST:
SELECT current_setting('TIMEZONE');
or with:
show timezone;
If it is not you can set it like this:
set timezone to est;
AS shown in this DEMO
If that is not working try with convert_timezone
select convert_timezone('US/Pacific', '2020-01-24 14:27:12')
And exploring the mater on hand I have found this fact:
Note Amazon Redshift doesn't validate POSIX-style time zone
specifications, so it is possible to set the time zone to an invalid
value. For example, the following command doesn't return an error,
even though it sets the time zone to an invalid value.
set timezone to ‘xxx36’;
from this source: https://docs.aws.amazon.com/redshift/latest/dg/CONVERT_TIMEZONE.html
'AT TIME ZONE' does not work like you are expecting. Use convert_timezone() instead.
SELECT
'2020-01-24 14:27:12' AT TIME ZONE 'US/Pacific' as foo,
-- expected '2020-01-24 6:27:12' got '2020-01-24 22:27:12+00'
convert_timezone('UTC', 'US/Pacific', CAST('2020-01-24 14:27:12' AS TIMESTAMP WITHOUT TIME ZONE)) as bar
-- expected '2020-01-24 6:27:12' got '2020-01-24 06:27:12'
;
'AT TIME ZONE' interprets the timestamp as being relative to the specified time zone and converts it to a TIMESTAMPTZ offset to UTC. That is in the above example it converts from US/Pacific to UTC, not the other way around.
It works perfectly fine for me (using dbVisualizer).
The issue is with your SQL Client.
SQL clients often impose formatting that impacts the values you see. You can test this by converting values to Text before sending them to your SQL client:
SELECT
'2020-01-24 14:27:12' AT TIME ZONE 'US/Pacific' as foo,
foo::text as t,
EXTRACT(HOUR FROM foo) as ex,
DATE_PART('HOUR', foo::timestamp) as dp
For me, this results in:
2020-01-24 22:27:12+00 2020-01-24 22:27:12+00 22.0 22.0
Try it in your SQL client and see what happens.
Related
I have been able to convert a TIMESTAMP field that is in UTC to CST using:
SELECT
TIMESTAMP(started_at) AS UTC,
TIMESTAMP_SUB(TIMESTAMP (started_at), INTERVAL 5 HOUR) AS CST
This returns:
ROW
UTC
CST
1
2020-05-17 13:07:22 UTC
2020-05-17 08:07:22 UTC
The second TIMESTAMP displays the correct date and time but UTC still shows. What is the simplest way to replace 'UTC' with 'CST' or, alternatively, remove 'UTC' altogether since I don't need the designation in the field itself?
You can use a plain sql replace function inline
select replace(TIMESTAMP_SUB(TIMESTAMP (started_at), INTERVAL 5 HOUR), 'UTC','') AS CST
The above searches the result of your expression (provided in your question) for 'UTC' and replaces it with nothing ''. You could also replace it with 'CST' as you noted.
Obligatory warning: I believe your query will only be correct half the year as long as DST is observed? You might want to look into sys.time_zone_info and its reference on the MSDN.
My advise is to convert the timestamp to a datetime local value:
select datetime(started_at, 'America/Chicago') as started_at_cst
Note that the time zone is not stored in the data value. Instead, this encodes the value in the string.
If you want to include the time zone value, I have found that the best approach is to use a string (argghh!). The following constructs a string:
format_timestamp('%F %X%z', started_at, 'America/Chicago') as started_at_str
which can be converted easily into a timestamp for date/time calculations:
timestamp(started_at_str)
I've fiddeling around with timestamps in PostgreSQL, reading a interesting Blog about this behavior, but have no clue to solve following problem:
How to select a 'timestamp with time zone' column with AT TIME ZONE from another column, including the offset to UTC in one step?
I've a sample table in PostgreSQL 10:
CREATE TABLE public.test_tz
(
id serial,
in_zone_timestamp timestamp without time zone,
in_zone character varying COLLATE pg_catalog."default",
CONSTRAINT test_tz_pkey PRIMARY KEY (id)
)
WITH (
OIDS = FALSE
)
TABLESPACE pg_default;
PostgreSQL's setting is
timezone=localtime
and the server runs at 'Europe/Berlin'
$ date --> Fri Mar 9 12:15:23 CET 2018
The timestamp column should store with this messy syntax:
INSERT INTO public.test_tz ( in_zone_timestamp, in_zone) VALUES
('2017-02-01 00:00:00' AT TIME ZONE current_setting('TIMEZONE') AT TIME ZONE 'Asia/Singapore', 'Asia/Singapore' );
If someone knows a better way, please don't hold back! The other solution is to use '2017-02-01 00:00:00-08' as the value, but I don't know the offset value.
I want to store the local timestamp like: 'The user hit a key at 2017-02-01 00:00:00 in Singapore'.
If I ask the database: Which time it was here in Europe, when the user in Singapore is hitting a key, I got:
SELECT in_zone_timestamp FROM public.test_tz;
--> '2017-01-31 17:00:00+01'
This seems OK, because Singapore has a offset of +8 hours.
If I want to know, which time it was in Singapore, I use:
SELECT in_zone_timestamp AT TIME ZONE in_zone FROM public.test_tz;
--> '2017-02-01 00:00:00'
That's OK too, but however, it doesn't return the offset to 'UTC', so I can't see that this timestamp is not in my local time!
I try some combinations of AT TIME ZONE or converting to timestamptz, but the results are not what I want. I expected a result like:
--> '2017-02-01 00:00:00+08'
At here, I only see one solution, to manually concat/convert/manipulate the result and add the offset by hand, but is this the only way?
Sorry if I explain this question a little bit too comlicated and hope someone can follow my thoughts.
Thanks in advance
The only way to have PostgreSQL convert a timestamp to a string like 2017-02-01 00:00:00+08 automatically is to change the session time zone:
SET timezone = 'Asia/Singapore';
You can use SET LOCAL to change the setting only for the duration of a transaction.
If you don't want that, you can get the offset with a query like this:
SELECT TIMESTAMP '2000-01-01 00:00:00' AT TIME ZONE 'UTC'
- TIMESTAMP '2000-01-01 00:00:00' AT TIME ZONE 'Asia/Singapore';
?column?
----------
08:00:00
(1 row)
Thanks for clarify, but in my opinion that PostgreSQL has a few shortcomings on this topic.
A 'not so perfect' solution for this problem is really to manually concat the parts needed.
SELECT (test_tz.in_zone_timestamp AT TIME ZONE in_zone) || (SELECT abbrev FROM pg_timezone_names WHERE name = in_zone) FROM public.test_tz;
--> 2017-02-01 00:00:00+08
This provides an acceptable solution, with small imperfections.
In some cases there is the timezone short text in the abbrev-column, like 'CET' or 'PDT' and not the +/- numeric value. This produces results (eg. for 'Europe/Berlin') like:
--> 2017-02-01 02:00:00CET
A better value gives the column 'utc_offset' of pg-timezone-names, but this requires a more complex text manipulation, I don't want at this point.
Second solution can be the manipulation of the output by application and formatting the text to whatever you need.
Hope that helps others to solve such problem without searching the internet for a not available support from the database.
Bye
I'm hurting my head again this :
On postgresql, I would like to get the local time for a given timezone.
So, at 15:45 GMT, I want 16:45 for +01:00, but I can't get the good anwser :
SQL Fiddle
Query 1:
select current_timestamp at time zone 'GMT' as time_local_gmt
Results:
| time_local_gmt |
|-----------------------------|
| 2018-01-26T15:45:10.871659Z |
This is OK.
Query 2:
select current_timestamp at time zone '+01:00' as time_local_paris
Results:
| time_local_paris |
|-----------------------------|
| 2018-01-26T14:45:10.871659Z |
This is totally wrong, seem like it's -01:00 instead of +01:00
Edit :
See the valid answer here : https://stackoverflow.com/a/48707297/5546267
This worked for me.
select current_timestamp at time zone 'UTC+1';
Gave me the following result.
2018-01-26T17:00:58.773039Z
There is also a list of timezone names.
Here is an excerpt from the PostgreSQL 9.6 documentation regarding timezone names.
The view pg_timezone_names provides a list of time zone names that are recognized by SET TIMEZONE, along with their associated abbreviations, UTC offsets, and daylight-savings status.
Basically, the following query will give you the current time in Paris.
SELECT current_timestamp AT TIME ZONE 'Europe/Paris';
Good Luck!
For completeness (even if #Avi Abrami's answer should be what you're searching for) let's take a look at the datetime operators in the docs.
One can use the INTERVAL keyword to add hours to the stored value:
SELECT current_timestamp AT TIME ZONE INTERVAL '+02:00' AS plus_two;
Which then results in
2018-01-26T17:45:10.871659Z
(when GMT time is 2018-01-26T15:45:10.871659Z)
Section 9.9.3 AT_TIME_ZONE mentions my use of INTERVAL without any preceeding operator:
In these expressions, the desired time zone zone can be specified either as a text string (e.g., 'PST') or as an interval (e.g., INTERVAL '-08:00'). In the text case, a time zone name can be specified in any of the ways described in Section 8.5.3.
The documentation says:
Another issue to keep in mind is that in POSIX time zone names, positive offsets are used for locations west of Greenwich. Everywhere else, PostgreSQL follows the ISO-8601 convention that positive timezone offsets are east of Greenwich.
I guess that is your problem.
Ok, finally found how to !
SELECT
current_timestamp
AT TIME ZONE 'GMT'
AT TIME ZONE '+01:00'
AS time_local_paris_right;
The timestamp is UTC without TZ by default, you force it as a GMT one, and then the second AT convert it with the right offset to give you the local time for the specified time zone.
SQL Fiddle
PostgreSQL 9.6 Schema Setup:
Query 2:
select current_timestamp at time zone 'GMT' as time_local_gmt
Results:
| time_local_gmt |
|-----------------------------|
| 2018-02-09T13:44:56.824107Z |
Query 3:
select current_timestamp at time zone '+01:00' as time_local_paris_wrong
Results:
| time_local_paris_wrong |
|-----------------------------|
| 2018-02-09T12:44:56.824107Z |
Query 4:
select current_timestamp at time zone 'GMT' at time zone '+01:00' as time_local_paris_right
Results:
| time_local_paris_right |
|-----------------------------|
| 2018-02-09T14:44:56.824107Z |
I would like to insert time data type in postgresql that includes the timezone and is aware of daylight savings time. This is what I have done:
CREATE TABLE mytable(
...
start_time time(0) with time zone,
end_time time(0) with time zone
)
INSERT INTO mytable(start_time, end_time)
VALUES(TIME '08:00:00 MST7MDT', TIME '18:00:00 MST7MDT')
I get the following error:
invalid input syntax for type time: "08:00:00 MST7MDT"
It works if I use 'MST' instead of 'MST7MDT', but I need it to be aware of DST. I also tried using 'America/Edmonton' as the timezone, but I got the same error.
What is the proper way to insert a time value (not timestamp) with timezone and DST?
EDIT:
I would actually like to use the 'America/Edmonton' syntax
The proper way is not to use time with time zone (note the space between time and zone) at all, since it is broken by design. It is in the SQL standard, so Postgres supports the type - but advises not to use it. More in this related answer:
Accounting for DST in Postgres, when selecting scheduled items
Since you are having problems with DST, timetz (short name) is a particularly bad choice. It is ill-equipped to deal with DST. It's impossible to tell whether 8:00:00 is in winter or summer time.
Use timestamp with time zone (timstamptz) instead. You can always discard the date part. Simply use start_time::time to get the local time from a timestamptz. Or use AT TIME ZONE to transpose to your time zone.
Generally, to take DST into account automatically, use a time zone name instead of a time zone abbreviation. More explanation in this related question & answer:
Time zone names with identical properties yield different result when applied to timestamp
In your particular case, you could probably use America/Los_Angeles (example with timestamptz):
INSERT INTO mytable(start_time, end_time)
VALUES
('1970-01-01 08:00:00 America/Los_Angeles'
, '1970-01-01 18:00:00 America/Los_Angeles')
I found this by checking:
SELECT * FROM pg_timezone_names
WHERE utc_offset = '-07:00'
AND is_dst;
Basics about time zone handling:
Ignoring time zones altogether in Rails and PostgreSQL
How about this?
INSERT INTO mytable(start_time, end_time)
VALUES('08:00:00'::time at time zone 'MST7MDT', '18:00:00'::time at time zone 'MST7MDT')
In Postgres, is it possible to change the default format mask for a timestamp?
right now comes back as
2012-01-03 20:27:53.611489
I would like resolution to minute like this:
2012-01-03 20:27
I know I can do this on individual columns with to_char() as or stripped down with a substr() by the receiving app, but having it formatted correctly initially would save a lot of work and reduce a lot of errors.
In PostgreSQL, The formatting of timestamps is independent of storage. One answer is to use to_char and format the timestamp to whatever format you need at the moment you need it, like this:
select to_char(current_timestamp, 'yyyy-MM-dd HH24:MI:SS.MS');
select to_timestamp('2012-10-11 12:13:14.123',
'yyyy-MM-dd HH24:MI:SS.MS')::timestamp;
But if you must set the default formatting:
Change the postgresql timestamp format globally:
Take a look at your timezone, run this as an sql query:
show timezone
Result: "US/Eastern"
So when you are printing out current_timestamp, you see this:
select current_timestamp
Result: 2012-10-23 20:58:35.422282-04
The -04 at the end is your time zone relative to UTC. You can change your timezone with:
set timezone = 'US/Pacific'
Then:
select current_timestamp
Result: 2012-10-23 18:00:38.773296-07
So notice the -07 there, that means we Pacific is 7 hours away from UTC. How do I make that unsightly timezone go away? One way is just to make a table, it defaults to a timestamp without timezone:
CREATE TABLE worse_than_fail_table
(
mykey INT unique not null,
fail_date TIMESTAMP not null
);
Then if you add a timestamp to that table and select from it
select fail_date from worse_than_fail_table
Result: 2012-10-23 21:09:39.335146
yay, no timezone on the end. But you want more control over how the timestamp shows up by default! You could do something like this:
CREATE TABLE moo (
key int PRIMARY KEY,
boo text NOT NULL DEFAULT TO_CHAR(CURRENT_TIMESTAMP,'YYYYMM')
);
It's a text field which gives you more control over how it shows up by default when you do a select somecolumns from sometable. Notice you can cast a string to timestamp:
select '2012-10-11 12:13:14.56789'::timestamp
Result: 2012-10-11 12:13:14.56789
You could cast a current_timestamp to timestamp which removes the timezone:
select current_timestamp::timestamp
Result: 2012-10-23 21:18:05.107047
You can get rid of the timezone like this:
select current_timestamp at time zone 'UTC'
Result: "2012-10-24 01:40:10.543251"
But if you really want the timezone back you can do this:
select current_timestamp::timestamp with time zone
Result: 2012-10-23 21:20:21.256478-04
You can yank out what you want with extract:
SELECT EXTRACT(HOUR FROM TIMESTAMP '2001-02-16 20:38:40');
Result: 20
And this monstrosity:
SELECT TIMESTAMP WITH TIME ZONE '2001-02-16 20:38:40-05' AT TIME ZONE 'EST';
Result: 2001-02-16 20:38:40
In postgres, you can change the default format mask for datetimes - using the set datestyle option; the available options can be found here (see 8.5.2. Date/Time Output).
Unfortunately, all the available options include the number of seconds - you will therefore need to reformat them either in the query or the application code (if applicable).
to_char() is used to create a string literal. If you want a different timestamp value, use date_trunc():
date_trunc('minute', now())
For converting literal input, use to_timestamp():
to_timestamp('2012-01-03 20:27:53.611489', 'YYYY-MM-DD HH24:MI')
This returns timestamptz. Cast to timestamp [without time zone] by appending ::timestamp (which assumes your current timezone setting), or with the AT TIME ZONE construct to define a time zone explicitly.
To my knowledge, there is no setting in PostgreSQL that would trim seconds from timestamp literals by default.