I am trying to use the add_month function but getting an error. I want to get the number of visits between [CAL_DATE - 13 months] and [CAL_DATE]. The format of the dates are as following: 2007-14, 2010-05, 2009-04 and etc. this is the error I am getting
"Bad time stamp external representation '2009-11"
and here is the code I am using. I can't seem to figure out the issue.
CAL_DATE BETWEEN add_months(CAL_DATE,-13) AND CAL_DATE.
I am using netezza database.
Presumably add_months expects a date as its first argument and returns a date. You don't have dates, you have YYYY-MM strings so you have two problems:
add_months won't know what to do with a YYYY-MM string.
BETWEEN won't know what to do with a date and a YYYY-MM string.
If you want to use add_months then you'll have to give it a date and convert the date it gives you to one of your YYYY-MM strings with something like this:
to_char(add_months((cal_date || '-01')::date, -13), 'yyyy-mm')
Appending -01 to your strings should give you a string representation of the first of that month and you should be able to cast that to a date with ::date. Then a to_char to convert the result of add_months back to your YYYY-MM format.
Alternatively, since add_months isn't really doing anything useful for you here, just use a PostgreSQL interval for the month adjustment:
to_char((cal_date || '-01')::date - interval '13 months', 'yyyy-mm')
Related
I am writing a function to pull the dates in the past 12 months. I am thinking to use (Current_date - 1month) for endubg month and (current_date -13months) for the beginning month.
However, when I use Current_date function, it returns me to the value 2022-12-29. Ideally, I would want the value to be 202212 in numeric forms because of my database. Beginning month should be 202112 and the ending month should be 202211. Is there a way I could do this in SQL?
We can use the TO_CHAR() function here:
SELECT TO_CHAR(CURRENT_DATE, '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 need to build a query in presto that could look back the trailing 70 days, the table I am working with is storing the dates in the format of 'YYYYMMDD'.
in postgresql, I can just simply write the where clause as
where date >= to_char(current_date - 70, 'YYYYMMDD')
and it'll pull in the date 70 days ago in a YYYYMMDD format.
However, in PrestoSQL, that function doesn't seem to exist, is there an alternative to this?
You can do this with date_format():
where date >= date_format(current_date - interval '70' day, '%Y%m%d')
Note that storing dates as strings is not a good practice at all - you should be using the proper date-like datatype - and then you won't need to do conversions at all.
You would just use date arithmetic:
where date >= current_date - interval '70' day
I'm not sure why you would want to involve strings in comparisons that are strictly date related.
For instance, I have a datetime like this '2016-04-02 00:00:00' and another like this '2016-04-02 15:10:00'. I don't care about the time-part, I want them to match just by the date-part.
I have tried with date(), to_date, datepart, nothing works.
Do it like this:
where yourField >= the start of your date range
and yourField < the day after the end of your date range
Edit starts here:
While you could use trunc, as suggested by others, bear in mind that filtering on function results tends to be slow.
Truncating the date to day should do the trick. Documentation here:
https://docs.oracle.com/cd/B19306_01/server.102/b14200/functions201.htm
For example
SELECT TRUNC(SYSDATE, 'DAY') FROM DUAL;
As others have said - there is no separate "date" data type in Oracle. A pure "date" is stored as a date with the time portion set to 00:00:00 (midnight at the beginning of the day), and TRUNC(date) will take any date and truncate the time to 00:00:00, so if you need to compare two dates you can write
where trunc(date_1) = trunc(date_2)
If your tables are very large and you need to do these comparisons often, this is not ideal, because wrapping column values within function calls (like date_1 within a TRUNC) prevents the use of an index you may have on the date_1 column. If you need to compare dates in two columns you may not have much of a choice, but if you compare to a fixed date (or something like SYSDATE) you may be better off with something like
where date_1 >= trunc(sysdate) and date_1 < trunc(sysdate) + 1
Here you are not using trunc on the column value, so if there's an index on the column, Oracle is free to use it - and trunc(sysdate) is computed only once, not for every single row. "+1" by the way means "add one day".
TO_DATE converts a string to a date; if you apply TO_DATE to a value that is already a legitimate date, you will get unexpected results because Oracle will first convert your true date to a string and then back to date again, and since these conversions require a date FORMAT for strings, and the formats Oracle assumes for conversion from date to string and from string to date may not match, .... you get the idea. As far as I know, DATE() (a FUNCTION) and DATEPART do not exist in Oracle; when you use a new language, keep Google close by and use it often.
If you input a date with no time component, for example TO_DATE('04-apr-2016, 'dd-mon-yyyy'), then the implicit time is 00:00:00 so you don't need to apply TRUNC() to it.
Good luck!
I want to insert the current date into one of the columns of my table. I am using the following:
to_date(SYSDATE, 'yyyy-mm-dd'));
This is working great, but it is displaying the year as '0014'. Is there some way that I can get the year to display as '2014'?
Inserting it as TRUNC(sysdate) would do. Date actually doesn't have a format internally as it is DataType itself. TRUNC() actualy will just trim the time element in the current date time and return today's date with time as 00:00:00
To explain what happened in your case.
say ur NLS_DATE_FORMAT="YY-MM-DD"
The Processing will be like below
select to_date(to_char(sysdate,'YY-MM-DD'),'YYYY-MM-DD') from dual;
Output:
TO_DATE(TO_CHAR(SYSDATE,'YY-MM-DD'),'YYYY-MM-DD')
January, 22 0014 00:00:00+0000
2014 - gets reduced to '14' in first to_char() and later while converted again as YYYY.. it wil be treated as 0014 as the current century detail is last!
to_date is used to convert a string to a date ... try to_char(SYSDATE, 'yyyy-mm-dd') to convert a date to a string.
The to_date function converts a string to a date. SYSDATE is already a date, so what this will do is to first convert SYSDATE to a string, using the session's date format as specified by NLS settings, and then convert that string back to date, using your specified date format (yyyy-mm-dd). That may or may not give correct results, depending on the session's NLS date settings.
The simple and correct solution is to skip the to_date from this and use SYSDATE directly.
Try this to_date(SYSDATE, 'dd-mm-yy')