Solved

Subtracting & Comparing Dates In MS Access

Posted on 2003-11-07
6
1,279 Views
Last Modified: 2008-02-01
Hello,

I would basically like to know if/how to subtract two dates in MS Access inorder to get the number of days between those dates.

Also how to compare two dates to make sure they are in the correct sequence (ie 11/12/2003 < 11/13/2003 <12/20/2004)   Please be specific as I know nothing about Access and its features.

Thanks
Moclab
0
Comment
Question by:Moclab
[X]
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
  • 3
  • 2
6 Comments
 
LVL 11

Accepted Solution

by:
Quetzal earned 500 total points
ID: 9705387
Subtraction:

Datediff(<interval>, <date1>, <date2>)

where <interval> is a string specifying the type of interval (hours, days, weeks, etc)...in this case "d" for days.
          <date1> less than <date2> returns the positive difference between the 2 dates

Using Abs obviates the need for compare dates:
Abs(Datediff("d", #11/12/2003#, #11/13/2003#)) = 1
Abs(Datediff("d", #11/13/2003#, #11/12/2003#)) = 1

Note: in Access we use the "#" notation to designate date constants.

If you had two database fields, Date1 and Date2, and want to calcuate the day difference in a query use:

Abs(Datediff("d",[Date1],[Date2]))
0
 
LVL 34

Expert Comment

by:Mike Eghtebas
ID: 9705439
Regarding you second question:

Re:>Also how to compare two dates to make sure they are in the correct sequence (ie 11/12/2003 < 11/13/2003 <12/20/2004)   Please be specific as I know nothing about Access and its features.

Table1
--------------
Date1                   Date2                  Date3
11/12/2003          11/13/2003          12/20/2004



Table2
----------------
Date
11/12/2003          
11/13/2003          
12/20/2004

Do you have your data like in Table1 or Table2? If like Table2, use:

Select Date From Table2 Order By Date

You need to make a query using above SQL (to do this, start any query, add a table to it, any table, from menu, select View/SQL and replace its content with above SQL).  But first make sure filed and table names are what you have.
----------
If you have Table1, use following SQL instead:

Select Date1 As Date From Table1 Union Select All Date2 As Date From Table1 Union Select All Date3 As Date From Table1 Order By Date

Either query will sort your date fields.

Mike
0
 

Author Comment

by:Moclab
ID: 9715897
Ok, I got the dates to subtract in a query but how do you put that number back into the table.

Tbl1(date1, date2, difference)
0
Enterprise Mobility and BYOD For Dummies

Like “For Dummies” books, you can read this in whatever order you choose and learn about mobility and BYOD; and how to put a competitive mobile infrastructure in place. Developed for SMBs and large enterprises alike, you will find helpful use cases, planning, and implementation.

 
LVL 34

Expert Comment

by:Mike Eghtebas
ID: 9716006
Why you want to do that?  This is not recommended.  Whenever you need the difference, vie it using just a query.  What if someone changes one of those datae in the table (without noticing the difference in days has to be changed at the same time).

Mike
0
 

Author Comment

by:Moclab
ID: 9716075
My problem is this:  I want the difference in the dates put in a difference column in the same table, so when I make a report (which prints the entire table) I can see the value of the difference in days.  Does access not automatically adjust the difference when a date is changed??
0
 
LVL 34

Expert Comment

by:Mike Eghtebas
ID: 9716399
I will give you the code for you future use.  But for this purpose, just build a query in top of your table.  In that query add a new field with alias name called NoOfDays wehre:

NoOfDays:Datediff("d",[Date1],[Date2])         'to avoid negative number, make sure
                                                                 '  [Date1]>[Date2] or use:      

NoOfDays:Abs(Datediff("d",[Date1],[Date2]))

This should work also:

NoOfDays:[Date1]-[Date2]  
-----------------
code to add to table (not recommended):

CurrentDB.Execute "Update MyTable Set NoOfDays=[Date1]-[Date2]"

Mike

0

Featured Post

MS Dynamics Made Instantly Simpler

Make Your Microsoft Dynamics Investment Count  & Drastically Decrease Training Time by Providing Intuitive Step-By-Step WalkThru Tutorials.

Question has a verified solution.

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

Describes a method of obtaining an object variable to an already running instance of Microsoft Access so that it can be controlled via automation.
AutoNumbers should increment automatically, without duplicates.  But sometimes something goes wrong, and the next AutoNumber value is a duplicate.  This article shows how to recover from this problem.
Familiarize people with the process of retrieving data from SQL Server using an Access pass-thru query. Microsoft Access is a very powerful client/server development tool. One of the ways that you can retrieve data from a SQL Server is by using a pa…
With Microsoft Access, learn how to specify relationships between tables and set various options on the relationship. Add the tables: Create the relationship: Decide if you’re going to set referential integrity: Decide if you want cascade upda…

729 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