The below works:
SELECT DATE_TRUNC('day', TIMESTAMP '2017-03-17 02:09:30')
But if I remove the "TIMESTAMP" part (as below) it doesn't. Why is this?
SELECT DATE_TRUNC('day', '2017-03-17 02:09:30')
From what I understand, the format should just be:
DATE_TRUNC('datepart', timestamp)
This simple format works in other situations..
The timestamp '2017-03-17' is a so-called timestamp-literal. The prefix timestamp is what makes this a timestamp and not a char. If you just have '2017-03-17', then it is a char-literal, which is not a timestamp, and DATE_TRUNC requires a datetime value.
Try this
select date_trunc('week', to_date('28/10/2020','dd/mm/yyyy'))
It will return date of monday for current week.
Related
I do not know when to use DATE_TRUNC and DATE_PART() in a query.
I have not really tried much, just some web searches that I do not fully grasp but I just started learning SQL (Postgres).
They both do very different things. One truncates a date to the precision specified (kind of like rounding, in a way) and the other just returns a particular part of a datetime.
From the documentation:
date_part():
The date_part function is modeled on the traditional Ingres equivalent
to the SQL-standard function extract:
date_part('field', source)
Note that here the field parameter needs to be a string value, not a
name. The valid field names for date_part are the same as for extract.
For historical reasons, the date_part function returns values of type
double precision. This can result in a loss of precision in certain
uses. Using extract is recommended instead.
SELECT date_part('day', TIMESTAMP '2001-02-16 20:38:40');
Result: 16
SELECT date_part('hour', INTERVAL '4 hours 3 minutes');
Result: 4
date_trunct():
The function date_trunc is conceptually similar to the trunc function
for numbers.
date_trunc(field, source [, time_zone ]) source is a value expression
of type timestamp, timestamp with time zone, or interval. (Values of
type date and time are cast automatically to timestamp or interval,
respectively.) field selects to which precision to truncate the input
value. The return value is likewise of type timestamp, timestamp with
time zone, or interval, and it has all fields that are less
significant than the selected one set to zero (or one, for day and
month).
...
Examples (assuming the local time zone is America/New_York):
SELECT date_trunc('hour', TIMESTAMP '2001-02-16 20:38:40');
Result: 2001-02-16 20:00:00
SELECT date_trunc('year', TIMESTAMP '2001-02-16 20:38:40');
Result: 2001-01-01 00:00:00
SELECT date_trunc('day', TIMESTAMP WITH TIME ZONE '2001-02-16 20:38:40+00');
Result: 2001-02-16 00:00:00-05
SELECT date_trunc('day', TIMESTAMP WITH TIME ZONE '2001-02-16 20:38:40+00', 'Australia/Sydney');
Result: 2001-02-16 08:00:00-05
SELECT date_trunc('hour', INTERVAL '3 days 02:47:33');
Result: 3 days 02:00:00
The following function returns dates in this format, "2021-01-01T00:00:00.000Z" and all I need is just the date portion of "2021-01-01".
DATE_TRUNC(‘day’, timestamp)
The return value from your current call to DATE_TRUNC already functionally is the date 2021-01-01, which in timestamp form is at midnight. That being said, if you want to view as a date only, then maybe you want this:
SELECT FORMAT_DATETIME("%Y-%m-%d", DATE_TRUNC('day', timestamp))
FROM yourTable;
Another trick which might work on BigQuery is to cast the timestamp to a VARCHAR of the right length:
SELECT CAST(DATE_TRUNC('day', timestamp) AS VARCHAR(10))
FROM yourTable;
How can I extract just the hour of a timestamp using standardSQL.
I've tried everything and no function works. The problem is that I have to extract the time from a column and this column is in the following format:2018-07-09T02:40:23.652Z
If I just put the date, it works, but if I put the column it gives the error below:
Syntax error: Expected ")" but got identifier "searchIntention" at [4:32]
Follow the query below:
#standardSQL
select TOTAL, dia, hora FROM
(SELECT cast(replace(replace(searchIntention.createdDate,'T',' '),'Z','')as
DateTime) AS DIA,
FORMAT_DATETIME("%k", DATETIME searchIntention.createdDate) as HORA,
count(searchintention.id) as Total
from `searchs.searchs2016626`
GROUP BY DIA)
Please, help me. :(
How can I extract just the hour of a timestamp using standardSQL?
Below is for BigQuery Standard SQL
You can use EXTRACT(HOUR FROM yourTimeStampColumn)
for example:
SELECT EXTRACT(HOUR FROM CURRENT_TIMESTAMP())
or
SELECT EXTRACT(HOUR FROM TIMESTAMP '2018-07-09T02:40:23.652Z')
or
SELECT EXTRACT(HOUR FROM TIMESTAMP('2018-07-09T02:40:23.652Z'))
In BigQuery Standard SQL, you can use the EXTRACT timestamp function in order to return an INT64 value corresponding to the part of the timestamp that you want to retrieve, like.
The available parts includes a full list that you can check in the documentation page linked, but in your use case you can directly refer to the HOUR operator in order to retrieve the INT64 representation of the hour value in a field of TIMESTAMP type.
#standardSQL
# Create a table
WITH table AS (
SELECT TIMESTAMP("2018-07-09T02:40:23.652Z") time
)
# Extract values from a Timestamp expression
SELECT
EXTRACT(DAY FROM time) as day,
EXTRACT(MONTH FROM time) as month,
EXTRACT(YEAR FROM time) as year,
EXTRACT(HOUR FROM time) AS hour,
EXTRACT(MINUTE FROM time) as minute,
EXTRACT(SECOND from time) as second
FROM
table
Is it possible to use the date_part function to extract a composite of multiple specifiers?
For example, I'd like to extract the month, day of month, and hour of day from a timestamp in the single string form "month:day-of-month:hour-of-day" so that
`SELECT date_part('day', TIMESTAMP '2001-02-16 20:38:40');`
would return "02:16:20"
This is much easier with to_char():
select to_char(TIMESTAMP '2001-02-16 20:38:40', 'MM:DD:HH24')
The documentation describes the formatting options.
How to get the date and time only up to minutes, not seconds, from timestamp in PostgreSQL. I need date as well as time.
For example:
2000-12-16 12:21:13-05
From this I need
2000-12-16 12:21 (no seconds and milliseconds only date and time in hours and minutes)
From a timestamp with time zone field, say update_time, how do I get date as well as time like above using PostgreSQL select query.
Please help me.
There are plenty of date-time functions available with postgresql:
See the list here
http://www.postgresql.org/docs/9.1/static/functions-datetime.html
e.g.
SELECT EXTRACT(DAY FROM TIMESTAMP '2001-02-16 20:38:40');
Result: 16
For formatting you can use these:
http://www.postgresql.org/docs/9.1/static/functions-formatting.html
e.g.
select to_char(current_timestamp, 'YYYY-MM-DD HH24:MI') ...
To get the date from a timestamp (or timestamptz) a simple cast is fastest:
SELECT now()::date
You get the date according to your local time zone either way.
If you want text in a certain format, go with to_char() like #davek provided.
If you want to truncate (round down) the value of a timestamp to a unit of time, use date_trunc():
SELECT date_trunc('minute', now());
This should be enough:
select now()::date, now()::time
, pg_typeof(now()), pg_typeof(now()::date), pg_typeof(now()::time)