Given a postgres table with a column that is a timestamp without time zone
select "columnWithoutTimeZone" from my_table
Which results in:
columnWithoutTimeZone
Jun 11, 2022, 1:15:06 AM
Jun 11, 2022, 1:15:06 AM
How can the date component of timestamp be extracted?
I tried
select to_date("columnWithoutTimeZone") from my_table
But this produced an error:
ERROR: function to_date(timestamp without time zone) does not exist
There is a similar stack question, but that deals with timezone conversions. I am simply trying to extract the Jun 11, 2022 that is presently represented in the column.
Thank you in advance for your consideration and response.
Does this work for you?
select "columnWithoutTimeZone"::date from my_table
Related
I'm trying to change an entire columns format into a smaller date format. I'm currently using PostgreSQL and need to change it from timestamp with timezone to an easier format, preferably one that just displays the year? How can I get this done?
Ive tried using to_char functions as well as date_parse to no avail. Im still very new to this so its stumping me at this point, any help is much appreciated
Wed Dec 31 2008 19:00:00 GMT -0500 (Eastern Time Zone) is the current format.
I just want to be able to turn that into the year, so 2008
Seeing that you're dealing with text, it's best to convert it to an actual timestamptz first, using to_timestamp(). Then you can alter the column, casting it in place: online demo
create table your_table(invoicedate text);
insert into your_table values
('Wed Dec 31 2008 19:00:00 GMT -0500 (Eastern Time Zone)');
alter table your_table
alter column invoicedate
type timestamptz using
(to_timestamp(invoicedate,'Dy Mon DD YYYY HH24:MI:SS AAA TZHTZM'));
alter table your_table
add column invoiceyear smallint;
update your_table set invoiceyear=extract(year from invoicedate);
Already mentioned extract() can get you the year out of a timestamptz.
Keep in mind that PostgreSQL will consume the timestamps and keep them internally as UTC. This means that if you want to process invoices differently based on their timezone of origin, you'll have to save that origin information in a separate column. Right now, extracting a year from that timestamp will give you 2009 instead of 2008, because that time in EST corresponds to 2009 in UTC. To get it as 2008, you'll have to read it as invoicedate at time zone 'EST'
I have trying to convert the UTC time to local time in Oracle Developer as per query below. I needed it in a particular format after conversion but after conversion to character the time comes out to be completely different. Can anyone tell me what am I doing wrong here please.
select e.encntr_id
,to_char(e.reg_dt_tm,'YYYY-MM-DD hh24:mm') as reg_dt_tm
,to_char(from_tz (cast(e.reg_dt_tm as timestamp),'UTC') at time zone
'Australia/Sydney','YYYY-MM-DD hh24:mm') as aest_reg_char
,from_tz (cast(e.reg_dt_tm as timestamp),'UTC') at time zone 'Australia/Sydney' as aest_reg
from encounter e
where e.ENCNTR_ID in(123)
encntr_id reg_dt_tm aest_reg_char aest_reg
123 2022-03-03 05:03 2022-03-03 16:03 03/MAR/22 04:51:12.000000000 PM AUSTRALIA/SYDNEY
Use TO_CHAR:
TO_CHAR(
from_tz (cast(e.reg_dt_tm as timestamp),'UTC') at time zone 'Australia/Sydney',
'YYYY-MM-DD hh24:mm:ss.ff TZR'
)
Or change the default TIMESTAMP_TZ format in SQL Developer:
ALTER SESSION SET NLS_TIMESTAMP_TZ_FORMAT = 'YYYY-MM-DD HH24:MI:SS.FF TZR';
and then run the query.
db<>fiddle here
Using PostgreSQL and trying to query a table that contains a UTC column. The UTC column is a column without the timezone as I understand it from the developer. Example in my DB for a record is (2021-08-26 13:59:26.867578). And I have to search for records that are between yesterday's date and today's date. When I tried the SQL statement below I get this error:
[42883] ERROR: operator does not exist: timestamp without time zone - integer Hint: No operator matches the given name and argument types. You might need to add explicit type casts. Position: 63
Here is my SQL statement for PostgreSQL:
SELECT omd.*
FROM "OCRMetaDatas" omd
WHERE (omd."ScannedAt")-5 BETWEEN Now()-1 and now()
ORDER BY omd."ScannedAt" desc;
Any help/direction would be appreciated. Thanks.
You can't operate integer with datetimes. Here you are trying to do that twice:
(omd."ScannedAt")-5
and
Now()-1
You should use INTERVAL with datetime there, such as:
SELECT omd.*
FROM "OCRMetaDatas" omd
WHERE (omd."ScannedAt")- '5 days'::INTERVAL BETWEEN Now()- '1 day'::INTERVAL and now()
ORDER BY omd."ScannedAt" desc;
As illustration of how to use at time zone:
--My TimeZone
show TimeZone;
TimeZone
------------
US/Pacific
select '2021-08-26 13:59:26.867578'::timestamp;
timestamp
----------------------------
2021-08-26 13:59:26.867578
select '2021-08-26 13:59:26.867578'::timestamp at time zone 'UTC';
timezone
-------------------------------
2021-08-26 06:59:26.867578-07
select now();
now
-------------------------------
2021-08-26 09:23:57.818477-07
at time zone will normalize the timestamps to the same time zone.
I have following value in my database:
Wed Jun 01 2016 00:00:00 GMT+0200 (CEST)
In my Code I got something like this:
2016-06-23
I need to query for a date like the one in my code, and in postgreSQL i found date_trunc to "cut off" unnecessary information from the date. The documentation shows following usage example:
SELECT date_trunc('hour', TIMESTAMP '2001-02-16 20:38:40');
Result: 2001-02-16 20:00:00
So I thougt this should work:
redshift.query("SELECT stuff, ts , date_trunc('day', TIMESTAMP 'ts') as 'date'
FROM ::table_name
WHERE date = :day",{table_name: name, day: day}, function(err, data){
>>>error: Redshift query Error: error: syntax error at or near "'date'"
But obviously this didn't work. It told me that I got a syntax error near the "day", I gues its the 'ts'. In all the examples I found, the timestamp was hardcoded, but that is not what I need. Any Ideas how to use it with a colum as timestamp instead of hardcode ?
You accidentally used a literal 'ts' instead of referencing column ts, it seems. Moreover, you cannot have a string literal like 'date' as column alias. It has to be an identifier.
So it should look like
date_trunc('day', TIMESTAMP ts) as "date"
Maybe you mixed up string literals (quoted with ') and identifiers (quoted with ").
I have a pair of programs that need to utilize a common timestamp while running. One program will be writing to Postgres tables with column type timestamp without time zone using now(). The other program will be writing to binary files using values returned from the gettimeofday() C function.
We are targeting two versions of Debian/Postgres. The first is Wheezy and Postgres 9.1. For quite some time we used the following functions to get common values:
C (compiled to program gettimeofday)
struct timeval tv;
memset(&tv, 0, sizeof(tv));
gettimeofday(&tv, NULL);
unsigned long val = tv.tv_sec * 1000000;
val += tv.tv_usec;
val /= 1000000;
printf("%lu\n", val);
psql
CREATE FUNCTION ms_ts(ts timestamp without time zone) RETURNS bigint
LANGUAGE sql IMMUTABLE STRICT
AS $_$select cast(round(1000 * extract('epoch' from $1)) as bigint);$_$;
This returned a common value that we could use. We aren't concerned with time zones--just about getting a common value between the two programs. When we moved to Debian Jessie and Postgres 9.4, it appears the behavior of this psql extract() function changed.
Machine 1, Debian Wheezy, Postgres 9.1, psql 9.1.20
date: Tue Mar 8 09:06:30 CST 2016
hwclock: Tue 08 Mar 2016 09:15:11 AM CST -0.375327 seconds
select now() -> 2016-03-08 09:07:23.183816-06
select extract('epoch' from cast('2016-03-08 09:00:08.277701' as timestamp without time zone));
-> 1457449208.2777
Machine 2, Debian Jessie, Postgres 9.4, psql 9.4.6
date: Tue Mar 8 09:06:31 CST 2016
hwclock: Tue 08 Mar 2016 09:15:12 AM CST -0.890904 seconds
select now() -> 2016-03-08 09:07:23.60542-06
select extract('epoch' from cast('2016-03-08 09:00:08.277701' as timestamp without time zone));
-> 1457427608.2777
So I researched and found that extract() has an option at time zone [...] to pick what time zone to extract the epoch with. Using 'uct' as the time zone seems to fix the issue on Jessie/Postgres 9.4, but it then messes up Wheezy/Postgres 9.1.
Machine 1, Debian Wheezy, Postgres 9.1, psql 9.1.20 (Values are off by six hours, likely based on local time zone CST)
select extract('epoch' from now() at time zone 'uct'); -> 1457579365
./gettimeofday -> 1457557765
Machine 2, Debian Jessie, Postgres 9.4, psql 9.4.6 (values match)
select extract('epoch' from now() at time zone 'uct'); -> 1457558544.44372
./gettimeofday -> 1457558543
What is the appropriate way to use extract() to match gettimeofday()? Or has the implementation just changed in such a way that I'll need two versions?
The "epoch" is the count of seconds since a fixed point. Traditionally on unix-based systems this is 1st January 1970, midnight at UTC.
Naturally if you change your timezone then it changes the difference from that fixed point. To be honest, I'm not sure the idea of measuring time since epoch without a timezone makes much sense. Actually, I've never really found the whole "timestamp without time zone" thing much use.
So - always provide a timezone if you want an absolute point in time (like you do in this case).
richardh=> SELECT extract(epoch from '1970-01-01 00:00:00+00'::timestamptz);
date_part
-----------
0
(1 row)
richardh=> SELECT extract(epoch from '1970-01-01 00:00:00+01'::timestamptz);
date_part
-----------
-3600
(1 row)
Ok this is apparently just a behavior change of the extract() function.
http://www.postgresql.org/docs/9.5/static/release-9-2.html
Make EXTRACT(EPOCH FROM timestamp without time zone) measure the epoch
from local midnight, not UTC midnight (Tom Lane)
This change reverts an ill-considered change made in release 7.3.
Measuring from UTC midnight was inconsistent because it made the
result dependent on the timezone setting, which computations for
timestamp without time zone should not be. The previous behavior
remains available by casting the input value to timestamp with time
zone.
So this implementation will work across platforms:
CREATE FUNCTION ms_ts(ts timestamp without time zone) RETURNS bigint
LANGUAGE sql IMMUTABLE STRICT
AS $_$select cast(round(1000 * extract('epoch' from $1::timestamptz)) as bigint);$_$;
I don't really care whether the result factors in time zone or not, just that it behaves the same as gettimeofday().
Addendum: Another factor is the internal timezone that Postgres is set to. This can be viewed by using:
show timezone;
If it's not 'localtime' then the value won't match gettimeofday(). To set to localtime for a given user use:
alter user yourusername set timezone='localtime';