Hi!
I have a dataset with id:chararray and date:chararray. Now, I want to filter out the dataset to those rows which start with:
If the first day of the current month is Sunday, pick all the Sundays of the current month only.
Otherwise pick the last Sunday of the previous month and all the Sundays of the current month.
So, for given below set
12456, 27-04-2014 (last Sunday of the previous month)
33578, 29-04-2014 (not Sunday)
43789, 04-05-2014 (Sunday)
57689, 06-05-2014 (not Sunday)
67890, 11-05-2014 (Sunday)
67845, 13-05-2014 (not Sunday)
57689, 18-05-2014 (Sunday)
33578, 25-05-2014 (Sunday)
The output would be
12456, 27-04-2014 (last Sunday of the previous month)
43789, 04-05-2014 (Sunday)
67890, 11-05-2014 (Sunday)
57689, 18-05-2014 (Sunday)
33578, 25-05-2014 (Sunday)
So, is there a way I can easily get to find the Sundays of the current month and if the first day of the month is not Sunday pick the last Sunday from previous month.
I have all the Date functions available for me like DaysBetween and GetDay in Pig.
From Apache PIG: Get the day of the week and split accordingly
(DaysBetween(ToDate('03-10-2013','dd-MM-YYY'),ToDate(0L)) + 4L) % 7
You can then filter on the returned value
Related
I am working on a MODE Case Study which can be accessed here https://mode.com/sql-tutorial/a-drop-in-user-engagement/#the-problem.
I am trying to access Table 2: Events which has a date column 'occurred_at'. I wanted to check the time frame of this case study, that is weeks and months.
I wrote a simple query
select distinct(date_trunc('week', occurred_at)) as week, date_trunc('month', occurred_at) as month
from tutorial.yammer_events
where event_type = 'engagement'
order by week;
and to my surprise, the first week of '2014-04-28' showed the month 'May' instead of 'April.
Can someone please tell me what is the reason for this?
Thank you
The PostgreSQL date_trunc rolls up the date to the first instance of the date depending upon the granularity (day, week, month, etc.)
For month this instance is the first day of month i.e. Day 1.
For week this instance is the first day of week i.e. Monday.
Suppose the date is 4th July 2021 which is Sunday, then the date_trunc will result in 1st July 2021 for month and 28th June 2021 for week which is Monday inside that week.
Suppose the date is 5th July 2021 which is Monday itself, then the date_trunc will still result in 1st July 2021 for month but result in 5th July 2021 for week since it is already Monday.
select extract(week from current_date) is giving 16 but current ISO week is 17.
Is this a bug or am I doing something wrong? Last week it worked OK.
You might be looking for:
extract(isoweek from current_date)
As per the documentation:
WEEK: Returns the week number of the date in the range [0, 53]. Weeks begin with Sunday, and dates prior to the first Sunday of the year are in week 0.
ISOWEEK: Returns the ISO 8601 week number of the date_expression. ISOWEEKs begin on Monday. Return values are in the range [1, 53]. The first ISOWEEK of each ISO year begins on the Monday before the first Thursday of the Gregorian calendar year.
I need get Monday of last week E.g
Today is 28/11/18 (wednesday)
I need get 19/11/18 (monday)
I know that I can obtain Monday of the current week with
val monday = DateTime().withDayOfWeek(DateTimeConstants.MONDAY)
I get it!
DateTime().withWeekOfWeekyear(
DateTime().weekOfWeekyear-1)
.withDayOfWeek(DateTimeConstants.MONDAY)
I only have to get the week of the year and subtract one week and that is all
I need to print the last sunday of the year from which adding 7 to it will give me all the sundays of next year.
I have the code to print all sundays for a particular year if i have a start date but i need the user to put the year so that last sunday of the previous year will be generated and 7 will be added to get first sunday of that year and so on till it reaches last sunday of next year
For example input year is 2017 it will check the last sunday of 2016 and add 7 to it to get first sunday of 2017 which is 1-1-2017 and it will go on printing all sundays till it reaches 31st december 2017
The function next_day() takes two arguments: a date and the name of a day of the week. It returns the closest "next" day (following the date argument) that matches the given day of the week. So the result is between one and seven days forward. (If you want 'Tuesday' and the input date is a Tuesday, the function returns the date seven days later.)
If you want the last Sunday of a year, it will be between Dec. 25 and Dec. 31. So if you call the next_day() function with the arguments Dec. 24 (!!) and 'Sunday' you'll get what you want.
The result will have the same time-of-day as the date argument, so if you give a date without a time-of-day, so will be the output (which is probably what you want). So:
select next_day(date '2016-12-24', 'Sunday') from dual;
NEXT_DAY(D
----------
2016-12-25
Added: If you take an input from your user, as a bind variable, you can do something like this:
select next_day(to_date(:input_year - 1 || '-12-24', 'yyyy-mm-dd'), 'Sunday') from dual;
If you provide 2017 as input (whatever mechanism your interface has for bind variables), the output will be 2016-12-25 (in DATE data type, so don't ask "in what format" - dates don't have a format!)
Why when I run
select (EXTRACT(WEEK FROM current_date)::int )
The output is 6 - why?
Today is 2016-02-14 which is the 8th week since the start of this year.
Am I getting this result wrong?
I'm looking for a function which I give it date and it tells me what week of the year this date is.
The documentation is pretty clear on the calculation:
week
The number of the ISO 8601 week-numbering week of the year. By
definition, ISO weeks start on Mondays and the first week of a year
contains January 4 of that year. In other words, the first Thursday of
a year is in week 1 of that year.
In the ISO week-numbering system, it is possible for early-January
dates to be part of the 52nd or 53rd week of the previous year, and
for late-December dates to be part of the first week of the next year.
For example, 2005-01-01 is part of the 53rd week of year 2004, and
2006-01-01 is part of the 52nd week of year 2005, while 2012-12-31 is
part of the first week of 2013. It's recommended to use the isoyear
field together with week to get consistent results.
Weeks start on a Monday, so Sunday is the end of a week (and "today" is Sunday where I am and in most of the world at this particular time). Also, the first week depends on the when the year starts.