Is there a way to find the number of days in a month in DB2. For example I have a datetime field which I display as Jan-2020, Feb-2020 and so on. Based on this field I need to fetch the number of days for that month. The output should be something like below table,
I'm using the below query
select reportdate, TO_CHAR(reportdate, 'Mon-YYYY') as textmonth from mytable
Expected output
ReportDate textMonth No of Days
1-1-2020 08:00 Jan-2020 31
1-2-2020 09:00 Feb-2020 29
12-03-2020 07:00 Mar-2020 31
Try this:
/*
WITH MYTABLE (reportdate) AS
(
VALUES
TIMESTAMP('2020-01-01 08:00:00')
, TIMESTAMP('2020-02-01 09:00:00')
, TIMESTAMP('2020-03-12 07:00:00')
)
*/
SELECT reportdate, textMonth, DAYS(D + 1 MONTH) - DAYS(D) AS NO_OF_DAYS
FROM
(
SELECT
reportdate, TO_CHAR(reportdate, 'Mon-YYYY') textMonth
, DATE(TO_DATE('01-' || TO_CHAR(reportdate, 'Mon-YYYY'), 'dd-Mon-yyyy')) D
FROM MYTABLE
);
Db2 has the function DAYS_TO_END_OF_MONTH and several others which you could use. Based on your month input, construct the first day of the month. This should be something like 2020-01-01 for Jan-2020 or 2020-02-01 for Feb-2020. Follow the link for several other conversion functions which allow you to transform between formats and to perform date arithmetics.
convert your column to a proper date and try this: day(last_day(date_column))
Related
I want to get month value using week no. I have week numbers stored in a table with year value
How to query database to get month value using that week value.
I am using hiveQL.
Eample:
201801(week) ------->201801(month)
201804(week) ------->201801(month)
Suppose week has full 7 days. Extract week number, multiply 7, add to 'year-01-01' and extract month from result date, lpad with 0 to get '01' from 1 and concatenate with year:
with data_example as(
select stack(3,'201801','201804','201805') as yr_wk
)
select yr_wk, concat(substr(yr_wk, 1,4),
lpad(month(date_add(date(concat(substr(yr_wk, 1,4),'-01-01')),int(substr(yr_wk, 5,2))*7)),2,0)
) yr_mth
from data_example
Result:
yr_wk yr_mth
201801 201801
201804 201801
201805 201802
select MONTH (birth_date) ...
....
..
However this gives numeric values.
I need Jan , Sep ...
How can I do this ? Case birth_date when 1 then 'jan' when 2 then ... is too long
Any other efficient ways ?
You use several functions that provide the information that you need:
VARCHAR_FORMAT - http://pic.dhe.ibm.com/infocenter/db2luw/v10r5/topic/com.ibm.db2.luw.sql.ref.doc/doc/r0007110.html
SUBSTR - http://pic.dhe.ibm.com/infocenter/db2luw/v10r5/topic/com.ibm.db2.luw.sql.ref.doc/doc/r0000854.html
LCASE - http://pic.dhe.ibm.com/infocenter/db2luw/v10r5/topic/com.ibm.db2.luw.sql.ref.doc/doc/r0052924.html
Example
Select LCASE(SUBSTR(VARCHAR_FORMAT(birth_date,'Month'),1,4))
From ...
This works with Timestamp or date
If the values of that column are not a time stamp you will have to do a CASE statement. However, if it is a timestamp than maybe you can use the MONTHNAME function
Attendence
(
Stu_id int
Att_Id int
Att_Date datetime
Att_Num numeric(15,5)
)
This table basically contains attendence records. I am trying to find the logic to enter the rows for missing dates from 1 Jan 2012 till today.
Assume there is a single attendence record for this period row (1,1,'2012-05-06',1.20000). Then I would like to insert rows for each day from 1 Jan 2012 till today except the existing date with the same values for all the fields except the date field which should be the actual date.
I am trying to bulk insert all the rows but don't know how would I adjust the date field
and check for the existing date.
Thanks.
Try a stored procedure which loops through the dates.
Or better yet, make a dates table and select from that. This will be much faster. Something like:
INSERT INTO Attendence (Stu_id, Att_Id, Att_Date, Att_Num)
SELECT a.Stu_id, a.Att_Id, d.TheDate, a.Att_Num
FROM Attendence a
INNER JOIN Dates d ON d.TheDate BETWEEN '2012-01-01' AND GETDATE()
AND d.TheDate <> a.Att_Date
I would use the DateDiff function to figure out the amount of days inbetween the date in the function and the date in question. Make a DateTime variable and give it the value of 1 Jan 2012. Then set up a while loop that loops the amount of days from the DateDiff function.
In psuedo, the while loop would look something like this.
#DaysTill = DateDiff(days, 1/1/2012, #SomeDate)
While #DaysTill>0
##Check = Select Count(Att_Date) From Attendance where AttDate = DateAdd(days, #DaysTill, Jan 1st 2012)
IF ##Check = 0 THEN Insert Into Attendance VALUES #Stu, #Id, DateAdd(days, #DaysTill, Jan 1st 2012), #numeric
#DaysTill = #DaysTill - 1
END
The main things are understanding DateAdd and DateDiff. After that everything becomes relatively simple.
Let's say that I have a range of SQL tables that are named name_YYYY_WW where YYYY = year and WW = week number. If I call upon a function that guides a user defined date to the right table.
If the date entered is "20110101":
SELECT EXTRACT (WEEK FROM DATE '20110101') returns 52 and
SELECT EXTRACT (YEAR FROM DATE '20110101') returns 2011.
While is nothing wrong with these results I want "20110101" to either point to table name_2010_52 or name_2011_01, not name_2011_52 as it does now when I concanate the results to form the query for the table.
Any elegant solutions to this problem?
The function to_char() will allow you to format a date or timestamp to output correct the iso week and iso year.
SELECT to_char('2011-01-01'::date, 'IYYY_IW') as iso_year_week;
will produce:
iso_year_week
---------------
2010_52
(1 row)
You could use a CASE:
WITH sub(field) AS (
SELECT CAST('20110101' AS date) -- just to test
)
SELECT
CASE
WHEN EXTRACT (WEEK FROM field ) > 1 AND EXTRACT (MONTH FROM field) = 1 AND EXTRACT (DAY FROM field) < 3 THEN 1
ELSE
EXTRACT (WEEK FROM field)
END
FROM
sub;
I get to dust off my VBScript hat and write some classic ASP to query a SQL Server 2000 database.
Here's the scenario:
I have two datetime fields called fieldA and fieldB.
fieldB will never have a year value that's greater than the year of fieldA
It is possible the that two fields will have the same year.
What I want is all records where fieldA >= fieldB, independent of the year. Just pretend that each field is just a month & day.
How can I get this? My knowledge of T-SQL date/time functions is spotty at best.
You may want to use the built in time functions such as DAY and MONTH. e.g.
SELECT * from table where
MONTH(fieldA) > MONTH(fieldB) OR(
MONTH(fieldA) = MONTH(fieldB) AND DAY(fieldA) >= DAY(fieldB))
Selecting all rows where either the fieldA's month is greater or the months are the same and fieldA's day is greater.
select *
from t
where datepart(month,t.fieldA) >= datepart(month,t.fieldB)
or (datepart(month,t.fieldA) = datepart(month,t.fieldB)
and datepart(day,t.fieldA) >= datepart(day,t.fieldB))
If you care about hours, minutes, seconds, you'll need to extend this to cover the cases, although it may be faster to cast to a suitable string, remove the year and compare.
select *
from t
where substring(convert(varchar,t.fieldA,21),5,20)
>= substring(convert(varchar,t.fieldB,21),5,20)
SELECT *
FROM SOME_TABLE
WHERE MONTH(fieldA) > MONTH(fieldB)
OR ( MONTH(fieldA) = MONTH(fieldB) AND DAY(fieldA) >= DAY(fieldB) )
I would approach this from a Julian date perspective, convert each field into the Julian date (number of days after the first of year), then compare those values.
This may or may not produce desired results with respect to leap years.
If you were worried about hours, minutes, seconds, etc., you could adjust the DateDiff functions to calculate the number of hours (or minutes or seconds) since the beginning of the year.
SELECT *
FROM SOME_Table
WHERE DateDiff(d, '1/01/' + Cast(DatePart(yy, fieldA) AS VarChar(5)), fieldA) >=
DateDiff(d, '1/01/' + Cast(DatePart(yy, fieldB) AS VarChar(5)), fieldB)
Temp table for testing
Create table #t (calDate date)
Declare #curDate date = '2010-01-01'
while #curDate < '2021-01-01'
begin
insert into #t values (#curDate)
Set #curDate = dateadd(dd,1,#curDate)
end
Example of any date greater than or equal to today
Declare #testDate date = getdate()
SELECT *
FROM #t
WHERE datediff(dd,dateadd(yy,1900 - year(#testDate),#testDate),dateadd(yy,1900 - year(calDate),calDate)) >= 0
One more example with any day less than today
Declare #testDate date = getdate()
SELECT *
FROM #t
WHERE datediff(dd,dateadd(yy,1900 - year(#testDate),#testDate),dateadd(yy,1900 - year(calDate),calDate)) < 0