To query the last 7 days from today in as400 as it stores the dates in char type how to retrieve the results from today as i tried using such as
where chardate >= char(days(curdate()) + 7)
but its still not working
There are two parts to the answer. The first involves date math on this particular flavor of DB2. The DB2 expression equivalent to curdate()) + 7 is current date + 7 days.
The second involves converting date values to character values (or vice versa) so we can compare them. We need to know what format chardate stores dates in before we can really crack that one. Let's assume it's in YYYY-MM-DD format. Then you can use char(current date + 7 days, iso) to get seven days in the future in the same format.
So, with that assumption, your where statement would be
where chardate >= char(current date + 7 days, iso)
There are several standard date formats that date can convert to:
ISO: YYYY-MM-DD
USA: MM/DD/YYYY
EUR: DD.MM.YYYY
JIS: YYYY-MM-DD
If your chardate is in a different format, you will need to do some rather fiddly work with substr. For example, to convert YYYY-MM-DD to YYYYMMDD you'd need something like
substr(char(current date, iso), 1, 4) ||
substr(char(current date, iso), 5, 2) ||
substr(char(current date, iso), 7, 2)
A major problem with this method is that formats that aren't stored in "year month day" order can't be reliably compared. That is, 12311969 (i.e., MMDDYYYY) will compare as greater than 01012011, since as far as the database is concerned, you're comparing two eight-digit numbers. (That's why you should almost always store dates in actual date fields or in YYYYMMDD or similar properly ordered format.)
I've had great success using a free utility called idate, which provides SQL user-defined functions (UDFs) to convert dates stored in char & numeric fields into dates. Note that this solution requires the availability of an RPG compiler.
For the last 7 days from today:
where
date(substr(chardate,1,4) || '-' ||
substr(chardate,5,2) || '-' ||
substr(chardate,7,2)) between current date - 7 days and current date
To perform a character range comparison:
where
chardate between
substr(char(current date - 7 days, iso),1,4) ||
substr(char(curernt date - 7 days, iso),6,2) ||
substr(char(current date - 7 days, iso),9,2)
and
substr(char(current date, iso),1,4) ||
substr(char(current date, iso),6,2) ||
substr(char(current date, iso),9,2)
Related
I am working locally with an sqllite DB. I have imported some records from teradata where there was a date field in the format of 'YYYY-MM-DD'. When i imported the records the date switched from a date to a number. I know this is a feature of sqllite and that one can access it via date(sqllite_date) when selecting it in a where clause.
My problem is that the dates now appear to be a bit odd. For example the year appears to be negative.
Is there anyway to recover this to the correct format?
Below is an example of converting a number in the database into a date
SELECT date(18386)
# -4662-03-28
SELECT datetime('now')
# 2021-02-11 10:41:52
SELECT date(sqllite_date) FROM mydb
# Returns -4662-03-28
# Should return 2020-05-04
I am very new to this area so apologies if this is a basic question. Thank you very much for your time
In SQLite you can store dates as TEXT, REAL or INTEGER.
It seems that you stored the dates in a column with INTEGER or REAL affinity.
In this case, if you use the function date(), it considers a value like 18386 as a Julian day, meaning the number of days since noon in Greenwich on November 24, 4714 B.C.
This is why date(18386) returns 4662-03-28B.C.
But I suspect that the date values that you have are the number of days since '1970-01-01'.
In this case, 18386 days after '1970-01-01' is '2020-05-04'.
So you can get the dates in the format YYYY-MM-DD if you add the value of your column as days to '1970-01-01':
SELECT date('1970-01-01', datecolumn || ' day') FROM tablename
Or by transforming your date values to seconds and treat them as UNIX time (the number of seconds since '1970-01-01 00:00:00 UTC'):
SELECT date(datecolumn * 24 * 3600, 'unixepoch') FROM tablename
Replace datecolumn with the name of your column.
I tried to group my daily data by week (given a reference date) to generate a smaller panel data set.
I used postgres before and there it was quite easy:
CREATE TABLE videos_weekly AS SELECT channel_id,
CEIL(DATE_PART('day', observation_date - '2016-02-10')/7) AS week
FROM videos GROUP BY channel_id, week;
But it seems like it is not possible to subtract a timestamp with a date string in Drill. I found the AGE function, which returns an interval between two dates, but how to convert this into an integer (number of days or weeks)?
DATE_SUB may help you here. Following is an example:
SELECT extract(day from date_sub('2016-11-13', cast('2015-01-01' as timestamp)))/7 FROM (VALUES(1));
This will return number of weeks between 2015-01-01 and 2016-11-13.
Click here for documentation
I have been trying with no success to to count how many values were created in a specific week day:
SELECT count(*) as count FROM packets WHERE strftime("%w", timeIn) = '1';
I have this values in timeIn
1472434822.60033
1472434829.12632
1472434962.34593
I don't know what I am doing wrong here.
furthermore, if I use this:
SELECT count(*) as count FROM packets WHERE strftime("%w", timeIn) = '6';
I get
2
which makes no sense. Thank you in advance.
You appear to be storing the date as the number of seconds since 1970 (the Unix epoch) - a common representation. The time strings accepted by the SQLite date functions (see the Time Strings section) default to interpreting numeric time strings as a Julian day numbers:
Similarly, format 12 is shown with 10 significant digits, but the date/time functions will really accept as many or as few digits as are necessary to represent the Julian day number.
You can see this with the following SELECT:
SELECT strftime('%Y-%m-%d', 1472428800.6) AS t
the result of which is:
4026-48-26
For your date representation to be interpreted as a Unix epoch, you need to include 'unixepoch' in the strftime call:
SELECT strftime('%Y-%m-%d', 1472428800.6, 'unixepoch') AS t
which returns:
2016-08-29
If you modify your SELECT to be:
SELECT count(*) as count FROM packets WHERE strftime("%w", timeIn, 'unixepoch') = '6'
you should see results more inline with your expectations.
I have a table called messages that stores messages from a chat with the following columns: username, message, datetime, where the type of datetime is TEXT and it is stored in the following format: "yyyy/MM/dd hh:mm:ss". I want to retrieve the average count of rows within a specific time range, without bothering with the date. For instance:
SELECT avg(count(message))
FROM messages
WHERE datetime < "2016/mm/dd 13:00:00" AND
datetime > "2016/mm/dd 12:00:00"
Is there some operator that allows any character to take the place of "mm" and "dd". Essentially, I am trying to construct a query that retrieves the average amount of messages within a specific time range, not the amount of messages on a specific date.
If I read your question correctly, you want to use your WHERE clause to restrict to any calendar date in 2016 between 12 and 13 hours. In this case, you can use STRFTIME to extract the year and hour in string format from your datetime column.
SELECT COUNT(message)
FROM messages
WHERE STRFTIME('%Y', datetime) = '2016' AND
STRFTIME('%H', datetime) < '13' AND
STRFTIME('%H', datetime) > '12'
Note that the reason while the inequalities should work with strings is because numerical strings still sort based on their lexigraphical order.
Update:
Since your datetime column is in a non standard format, you may be able to workaround this by substringing off the various pieces you need to use in the WHERE clause:
SELECT COUNT(message)
FROM messages
WHERE SUBSTR(datetime, 1, 4) = '2016' AND
SUBSTR(datetime, 12, 2) < '13' AND
SUBSTR(datetime, 12, 2) > '12'
I'd like to get this to work in Teradata:
Updated SQL for better example
select
case
when
current_date between
cast('03-10-2013' as date format 'mm-dd-yyyy') and
cast('11-03-2013' as date format 'mm-dd-yyyy')
then 4
else 5
end Offset,
(current_timestamp + interval Offset hour) GMT
However, I get an error of Expected something like a string or a Unicode character blah blah. It seems that you have to hardcode the interval like this:
select current_timestamp + interval '4' day
Yes, I know I hardcoded it in my first example, but that was only to demonstrate a calculated result.
If you must know, I am having to convert all dates and times in a few tables to GMT, but I have to account for daylight savings time. I am in Eastern, so I need to add 4 hours if the date is within the DST timeframe and add 5 hours otherwise.
I know I can just create separate update statements for each period and just change the value from a 4 to a 5 accordingly, but I want my query to be dynamic and smart.
Here's the solution:
select
case
when
current_date between
cast('03-10-2013' as date format 'mm-dd-yyyy') and
cast('11-03-2013' as date format 'mm-dd-yyyy')
then 4
else 5
end Offset,
(current_timestamp + cast(Offset as interval hour)) GMT
You have to actually cast the case statement's return value as an interval. I didn't even know interval types existed in Teradata. Thanks to this page for helping me along:
http://www.teradataforum.com/l081007a.htm
If I understand correctly, you want to multiply the interval by some number. Believe it or not, that's literally all you need to do:
select current_timestamp as right_now
, right_now + (interval '1' day) as same_time_tomorrow
, right_now + (2 * (interval '1' day)) as same_time_next_day
Intervals have always challenged me for some reason; I don't use them very often. But I've had this little example in my Teradata "cheat sheet" for quite a while.
Two remarks:
You could return an INTERVAL instead of an INT
The recommended way to write a date literal in Teradata is DATE 'YYYY-MM-DD' instead of CAST/FORMAT
select
case
when current_date between DATE '2013-03-10' and DATE '2013-11-03'
then interval '4' hour
else interval '5'hour
end AS Offset,
current_timestamp + Offset AS GMT