One of my columns is a date type in the following format: YYYY-MM-DD. I want to extract YYYY-MM. So far, the resources I've come across show me that I can extract either year using SELECT extract(year from order_date)... but I can't figure out how to extract both the year and the month. I tried the following but it didn't work: https://www.w3schools.com/sql/func_mysql_extract.asp
I just want to point out that it is often convenient to leave the value as a date. If so, use date_trunc():
select date_trunc('month', order_date) as yyyymm
If you really want a string, you should accept Nick's answer.
In PostgreSQL you can use TO_CHAR():
SELECT TO_CHAR(order_date, 'YYYY-MM')
Output (if order_date = '2020-04-06'):
2020-04
Note if your column is not already a date or timestamp you will need to cast it to a date or timestamp (e.g. order_date::date).
Demo on dbfiddle
Related
I have a snapshot date in the following format: 2021-06-28 and I would like to have it like that: 202106. So the first four digits is year and next two is the month with leading zero. I tried this code:
concat(extract(year from snapshot_date), extract(month from snapshot_date))
but I have in return: 20216, without leading zero. How can I easily get it without CASE statement?
Try format_date:
select format_date("%Y%m", snapshot_date)
from mytable
Assuming snapshot_date is of date data type - you can use recently introduced Format clause for CAST as in below example
select cast(snapshot_date as string format 'YYYYMM')
from `project.dataset.table`
if "snapshot_date" is in date format, then this should work
select to_char(snapshot_date, 'yyyymm') from table_name
As a note, you can return the value as a number and just use multiplication:
(extract(year from snapshot_date) * 100 + extract(month from snapshot_date)) as yyyymm
Can we use date_trunc for a date (not date-time) that we are trying to "truncate" (not sure if the term can be applied here) to e.g. the start of the week? So if I have date_trunc(week, 28/10/2020) and I want to get the start of the week that 28th of October lies in (so 26th of October)? I tried this in my SQL command line but I get error messages.
If I am doing: SELECT to_date ('02 Oct 2001', 'DD Mon YYYY'); How can I ensure the resulting format is in a date format I specify (rather than the default date format)? For example if I want it in format DD-MM-YYYY?
select to_char(date '2017-06-02', 'MM') < in this example, why do we need "date" for this to work? The general format for to_char should be TO_CHAR (timestamp_expression, 'format'). I don't see in this general format that we need "day".
if I have a WHERE filter like to_char(order_date, '20-10-2020'), and there are indeed some rows with this order date, will these rows still show in my results (after running query) if these rows are in DATE format (so 20 Oct is in date format) as opposed to string (which is what I am filtering by as I am doing to_char). I know there would be no need to use to_char in this case but just asking..
yes, you can use date in text form but you have to cast it to a correct type
these queries will work
select date_trunc('week', '2020-10-28'::date);
select date_trunc('week', '10/28/2020'::date);
-- as well as
select date_trunc('week', '2020-10-28'::datetime);
and return timestamp 2020-10-26 00:00:00.000000
note, next query
select date_trunc('week', '28/10/2020'::date);
will fail with error date/time field value out of range: "28/10/2020";
You can use to_char, it returns text, if you need a date format you have to case it again
select to_char( to_date ('02 Oct 2001', 'DD Mon YYYY'), 'DD-MM-YYYY')::date;
select to_char('02 Oct 2001'::date, 'DD-MM-YYYY')::date;
'2017-06-02' is a text and it can't be automatically converted to timestamp. Actually I don't know a text format which can.
No, you need to explicitly cast into date type to use it as a filter
where order_date = date_stored_as_a_text::date
I am answering the questions in a different order as there are some wrong assumptions:
Question 3
There is a general difference between '2017-06-02' and date '2017-06-02' - the first one is just a varchar, a string, NOT handled as a date by Redshift, the 2nd one tells Redshift to handle the string as date and therefore works.
Question 2
A date data type column has no format - you may an sql client that can display date columns in different formats, however, this is not a functionality of redshift. SELECT to_date ('02 Oct 2001', 'DD Mon YYYY'); tells redshift to convert the string '02 Oct 2001' to date.
Question 1
DATE_TRUNC('datepart', timestamp) also supports week as datepart - see Date parts for date or timestamp function (Also shown in the example of AWS). You should also be able to provide a date instead of a timestamp.
Question 4
to_char(order_date, '20-10-2020')is not a filter and you are using it wrong.
AWS TO_CHAR
TO_CHAR converts a timestamp or numeric expression to a character-string data format.
I guess you are rather looking for:
where to_char(order_date, 'YYYY-MM-DD') = '20-10-2020'
I am trying to use the Date_Trunc for MONTH function in a SQL statement but somehow it is not working for me. I am trying to pull entries which happen after April 1st, 2019. The raw date format from the Redshift database is this format which I am trying to group into month/year buckets: 2019-04-08T00:13:20.000Z
Input
SELECT
client_id as user_id,
session_utc as job_date --(format:2019-04-08T00:13:20.000Z)
FROM table1 as hits
WHERE job_date >= DATE_TRUNC('month', 2019-04-01)
group by 1,2;
Output
"ERROR: function date_trunc("unknown", integer) does not exist Hint: No function matches the given name and argument types. You may need to add explicit type casts."
What am I doing wrong?
The DATE_TRUNC Function - Amazon Redshift takes timestamp as input and provides a timestamp as output:
DATE_TRUNC('datepart', timestamp)
For example:
SELECT DATE_TRUNC('month', '2019-05-07'::timestamp)
2019-05-01 00:00:00
Therefore, your line should read:
WHERE job_date >= DATE_TRUNC('month', '2019-04-01'::timestamp)
If you wish to have the output as a date, append ::date:
SELECT DATE_TRUNC('month', '2019-05-07'::timestamp)::date
2019-05-01
Also, note that the date converts into a timestamp as at midnight. This can cause a difference for some comparisons. For example:
'2019-05-07 03:03:31.389324+00'::timestamp > '2019-05-07'::timestamp
will evaluate as True because it is comparing to midnight at the start of the day. This is different to comparing two dates (without timestamps).
The syntax for the function is DATE_TRUNC('datepart', timestamp), seems you need to use as DATE_TRUNC('month', session_utc)(this already truncates to the first date of April 2019 i.e. 2019-04-01 )
Assuming you are using Postgres, you need quotes around your date constant and can convert to the right types:
WHERE job_date >= DATE_TRUNC('month'::text, '2019-04-01'::date)
Here is a db<>fiddle.
I would like to the current date minus a previous begin date with the result with the result being the number days there is a difference of the two?
I have attempted the following: date_sub(Begindt, INTERVAL current_date)
Also, will I have to cast things differently?
Below is for BigQuery Standard SQL
DATE_DIFF(CURRENT_DATE(), Begindt, DAY)
See more for DATE_DIFF()
Above assumes the Begindt field is of DATE type
If not, you should cast to DATE type via CAST or PARSE_DATE functions
Are you finding something like below
DATE_DIFF(Begindt, CURRENT_DATE, day)
I need to change a date value that is coming from a table in the form of May2013 (MonYYYY). The column itself is a VARCHAR
In my select statement, I am looking to retrieve the previous month (Apr2013). I've done some research and found the following, if I were using SYSDATE:
select to_date(add_months(sysdate, 'MONYYY')-1) from dual
How do I make it work for the date structure I have above? I've tried:
select to_date(add_months(date.datetable, MONYYY)-1) from datetable
ADD_MONTHS function needs a date variable as input. So, first you need to convert your varchar column to date type and then apply the add_months function.
SELECT ADD_MONTHS (TO_DATE ('May2013', 'monyyyy'), -1) FROM DUAL;
The return type will be date. In this case, it returns 0th hour of first day of April.