I have to write an sql query where I need to extract data for 30 days minus few days,
something like this, datetime <= -5 days
what is the best possible way I can write in teradata?
Thanks in advance:)
Exactly 5 days based on a timestamp, e.g. 2021-09-24 13:42 -> 2021-09-19 13:42
where timestamp_column <= current_timestamp - interval '5' day
Full days starting at midnight:
where timestamp_column <= current_date - 5
Related
Let's say I have a column with values in the format of a datetime '2021-07-01 00:00:00.000', how do I get the last date of the week (Sunday) for any datetime such as this in sqlite3? The day of the last date of the week is a Sunday.
So the answer for this date would want something like 2021-07-04 or 2021/07/04 (removing the time part) which is the date of the Sunday for the week the date 2021-07-01 is belonging to.
I know how this can be done in sqlserver but I do not know how to do it in sqlite.
Could someone please assist me on this? Let me know if you need more clarification.
Here is my attempt on sqlserver, but i need to get the same result in sqlite
SELECT
somedate,
CONVERT(VARCHAR(10),DATEADD(DAY, 7 - DATEPART(WEEKDAY, [somedate]), [somedate]),111) AS Last_Date_Of_Week
FROM table
apparently i can't do this in sqlite because sqlite does not have an official datetime type.
Sqlite date and time functions consider Sunday to be the first day of the week, and have a weekday modifier to advance a given timestamp to the given day of the week (Using 0-based indexing from Sunday). So:
sqlite> SELECT date('2021-07-01 00:00:00.000', 'weekday 0');
date('2021-07-01 00:00:00.000', 'weekday 0')
--------------------------------------------
2021-07-04
This is the same query I used in the past for a DATE field, however for a DATETIME field it doesn't work.
SELECT
*
FROM
user_log
WHERE
log_updated = DATE_SUB(DATE(NOW()), INTERVAL 21 DAY);
I want a date from EXACTLY 21 days ago, but it can be of any time during that day. I do not want 21 days and over (or 21 days and under).
You can do the following:
SELECT
*
FROM
user_log
WHERE
DATE(log_updated) = DATE(NOW() - INTERVAL 21 DAY);
But then this is not an efficient (sargable) solution, as using a function on the Column will impede the usage of indexing (if defined).
So, a better approach would be:
SELECT
*
FROM
user_log
WHERE
log_updated >= DATE(NOW() - INTERVAL 21 DAY) AND
log_updated < DATE(NOW() - INTERVAL 20 DAY)
Notice that I have used a day after the required date for maximum bound checking (not inclusive). It is obtained by INTERVAL -20 DAY
Since DATE(NOW()) is the same as CURDATE(), you may as well use
WHERE log_updated >= CURDATE() - INTERVAL 21 DAY
AND log_updated < CURDATE() - INTERVAL 20 DAY
This may use an index on log_updated.
In contrast, DATE(log_updated) ... cannot use an index on log_updated.
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
I have a simple SQL for calculating week number in my reports on SQLite
SELECT STRFTIME('%W', 'date_column')
It was correct for 2009-2012. In 2013 I got always the wrong week number.
For example
SELECT STRFTIME('%W', '2012-02-28')
return '09' and this is correct.
SELECT STRFTIME('%W', '2013-02-28')
return '08' and this is wrong. We have the 9th week.
Is there something in SQLite date time functions that I don't understand? Or is it a bug of SQLite?
CL's answer works fine for OP's definition of "right", which is not quite the same as ISO definition. ISO week numbers are always in the range 1-53 (no week 0), and the last 3 days of a year may fall into Week 1 of the following year, just like the first 3 days may fall into Week 52 or 53 of the preceding year. To take these corner cases into account, you need to do something like:
SELECT
(strftime('%j', date(MyDate, '-3 days', 'weekday 4')) - 1) / 7 + 1 AS ISOWeekNumber
FROM MyTable;
As a side note, SQLite's Date and Time documentation does link to the POSIX strftime man page, which defines %W modifier as:
"week number of the year (Monday as the first day of the week) as a decimal number [00,53]. All days in a new year preceding the first Monday are considered to be in week 0."
To convert from SQLite's undocumented week definition (first week is the week with the year's first Monday in it, or the week with 7 January in it) to the ISO week definition (first week is the week with the year's first Tuesday in it, or the week with 4 January in it), we let SQLite compute the week of the year's 4 January. If that is not one, we have to increase the week number:
SELECT strftime('%W', MyDate)
+ (1 - strftime('%W', strftime('%Y', MyDate) || '-01-04'))
FROM MyTable
This has gotten me a little paranoid, but I'm retrieving a set of records that fall within a period of time, say, the period from the january 1, 2011 (starting at midnight) to march 31, 2011 (all records up to 11:59:59 PM)
I'm using the condition
t.logtime between to_date('2011-01-01', 'yyyy-mm-dd') and to_date('2011-03-31')
Note that logtime is a datetime field.
Does this reflect what I want? Or am I actually missing 24 hours less a second?
I could specify the time as well, but I was hoping I this could be done without it.
Yes, you are missing nearly all of the last day. There are various solutions; probablt the simplest is:
t.logtime >= to_date('2011-01-01', 'yyyy-mm-dd')
and t.logtime < to_date('2011-04-01', 'yyyy-mm-dd')
I'd use the ANSI date literal syntax too:
t.logtime >= date '2011-01-01'
and t.logtime < date '2011-04-01'
Another way is:
trunc(t.logtime) between date '2011-01-01' and date '2011-03-31'
but note that that can no longer use an index on logtime (though it can use an index on trunc(logtime)).