Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people, just like you, are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
Solved

Previous month date calculations

Posted on 2013-06-18
6
329 Views
Last Modified: 2013-06-19
Why following works for Feburary but not for april dates?  When @StarteDate is 4/15/13 and @EndDate is 4/30/13, @LPEndDate returns as '3/30/13' (it should return '3/31/13')? Any ideas?

declare       @NoOfMonths int,
             @LPStartDate datetime,
             @LPEndDate datetime,
             @StartDate datetime = '2/15/13',
             @EndDate datetime = '2/28/13'
             
set @NoOfMonths=DATEDIFF(M,@StartDate,@EndDate)+1

set @LPEndDate=DATEADD(m,-1,@EndDate)
set @LPStartDate =DATEADD(m,@NoOfMonths*-1,@StartDate)
if datepart(d,@LPEndDate) >15 and datepart(d,@LPEndDate) <29
begin
set @LPEndDate=DATEADD(ms,-3,DATEADD(mm,0,DATEADD(mm,DATEDIFF(mm,0,@EndDate),0)))
end
select @LPStartDate, @LPEndDate
0
Comment
Question by:theone1
  • 2
  • 2
  • 2
6 Comments
 
LVL 16

Expert Comment

by:Surendra Nath
ID: 39257417
I already have a solution for you in my blog post here, check it out
http://everysolution.wordpress.com/2011/08/25/how-to-find-the-last-day-of-the-month/
0
 
LVL 16

Accepted Solution

by:
Surendra Nath earned 250 total points
ID: 39257428
the only flaw in your logic over here is.. you are checking if the date is  < 29, if that is corrected then the expected comes out ...

declare       @NoOfMonths int,
             @LPStartDate datetime,
             @LPEndDate datetime,
             @StartDate datetime = '2/15/13',
             @EndDate datetime = '2/28/13'
             
--set @StartDate = '4/15/13'
--set @EndDate = '4/30/13'

set @StartDate = '3/15/13'
set @EndDate = '3/31/13'

set @NoOfMonths=DATEDIFF(M,@StartDate,@EndDate)+1

set @LPEndDate=DATEADD(m,-1,@EndDate)
set @LPStartDate =DATEADD(m,@NoOfMonths*-1,@StartDate)

if datepart(d,@LPEndDate) >15 and datepart(d,@LPEndDate) <=31
begin
set @LPEndDate=DATEADD(ms,-3,DATEADD(mm,0,DATEADD(mm,DATEDIFF(mm,0,@EndDate),0)))
end
select @LPStartDate, @LPEndDate 

Open in new window

0
 

Author Closing Comment

by:theone1
ID: 39257455
Strange when I first had @LPEndDate <=30 it didnt work,,,,, but hey,,,, you are the one to solve it for me,,,, THANK YOU!!!
0
VMware Disaster Recovery and Data Protection

In this expert guide, you’ll learn about the components of a Modern Data Center. You will use cases for the value-added capabilities of Veeam®, including combining backup and replication for VMware disaster recovery and using replication for data center migration.

 
LVL 48

Expert Comment

by:PortletPaul
ID: 39258233
my only contribution here will be - why look for the last day of a month?

this is a guess, but what this often stems from is someone using this date arithmetic for use in a date range filter
e.g.
select <<whatever>>
from <<whereever>>
where some_date between {first day of period} and {last day of period}

while this can be workable, often a simpler - AND more reliable method is to avoid using 'between', like so:

select <<whatever>>
from <<whereever>>
where some_date >= {first day of period}
    and some_date <   {first day of next period}

i.e. it's quite easy to get the first day of any month (it's always 1)
and by using <   {first day of next period}
we don't have to concern ourselves with times during the {last day of month}

forgive me if this is utterly irrelevant here - it's a topic of interest to me.
0
 

Author Comment

by:theone1
ID: 39261322
hey P Paul, thank you for explanation.... makes much sense :) you are good teacher sir!
0
 
LVL 48

Expert Comment

by:PortletPaul
ID: 39261369
:) too kind

if you need more on this topic please see: "Beware of Between"
0

Featured Post

Free Tool: Port Scanner

Check which ports are open to the outside world. Helps make sure that your firewall rules are working as intended.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Audit has been really one of the more interesting, most useful, yet difficult to maintain topics in the history of SQL Server. In earlier versions of SQL people had very few options for auditing in SQL Server. It typically meant using SQL Trace …
I have written a PowerShell script to "walk" the security structure of each SQL instance to find:         Each Login (Windows or SQL)             * Its Server Roles             * Every database to which the login is mapped             * The associated "Database User" for this …
In a recent question (https://www.experts-exchange.com/questions/29004105/Run-AutoHotkey-script-directly-from-Notepad.html) here at Experts Exchange, a member asked how to run an AutoHotkey script (.AHK) directly from Notepad++ (aka NPP). This video…

789 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question