[Okta Webinar] Learn how to a build a cloud-first strategyRegister Now

x
?
Solved

Yet another OleDBDataAdapter quirk, the EMPTY(FIELDNAME) condition

Posted on 2006-06-21
7
Medium Priority
?
204 Views
Last Modified: 2010-04-23
Take a simple select.

SELECT ID, LAST, FIRST, ORDER
FROM TABLE
WHERE ORDER IS NULL

This will not work in the table I am pulling from because the field is not actually NULL it is blank. For some reason blank and NULL are not the same, maybe tonight after a few glasses of Jack Daniels that will make sense to me. So according to my friend Google the usage of EMPTY(ORDER) should work and behold in the Query Builder is does run !! The problem is when you hit ok it says the select statement cannot be generated. I manually do the select statement in the code, and it still does not run. Am I missing something ?
0
Comment
Question by:ParanoidOne
  • 4
  • 3
7 Comments
 

Author Comment

by:ParanoidOne
ID: 16952882
Oh by the way, what happens when I manually edit the select statement in the code is after launch the dataset comes up empty.
0
 

Author Comment

by:ParanoidOne
ID: 16952942
Ok think I figured it out.

SELECT ID, LAST, FIRST, ORDER
FROM TABLE
WHERE ORDER <> {  /  /    }
0
 
LVL 52

Expert Comment

by:Carl Tawn
ID: 16952960
Have you tried:

    SELECT ID, LAST, FIRST, ORDER
    FROM TABLE
    WHERE ORDER = ''

?

P.S.

    The difference between NULL and empty is that NULL represents a value that has never been set rather than simply not currently having a value. As an example, consider a Table that store the last time a user logged in. If the LastLoggedIn field has a NULL value then this indicates that the user has never signed in.

P.P.S.

    Ideally you shouldn't allow a field to contain NULL unless the NULL-ness actually means something.
0
VIDEO: THE CONCERTO CLOUD FOR HEALTHCARE

Modern healthcare requires a modern cloud. View this brief video to understand how the Concerto Cloud for Healthcare can help your organization.

 

Author Comment

by:ParanoidOne
ID: 16953613
So you are saying in my new database always have the fields with something, just not NULL ? Having NULL fields are a bad practice then ? I will post again in a sec after this has run and let you know if that works too.
0
 
LVL 52

Expert Comment

by:Carl Tawn
ID: 16953684
Using NULL isn't bad practice, its just that a lot of people use NULL when they shouldn't do.

As I mentioned in my previous post, you should really only allow NULL when it means something (i.e. the difference between not currently having a value and never having been set).

If you disallow NULL for text based fields then they will default to an empty string, which also removes the problem of having to check for both NULL and empty.
0
 

Author Comment

by:ParanoidOne
ID: 16953770
What about Date Fields, is that also bad practice ?
0
 
LVL 52

Accepted Solution

by:
Carl Tawn earned 2000 total points
ID: 16953807
Date fields are one of the more common places to allow NULL. Because, with Dates a NULL provides the distinction between having never been set and having an arbitary value.

Again, it all depends on whether you need to tell the difference between the value having never been set or not. If you don't need to know if it has ever been set or not then you shouldn't use NULL.
0

Featured Post

Important Lessons on Recovering from Petya

In their most recent webinar, Skyport Systems explores ways to isolate and protect critical databases to keep the core of your company safe from harm.

Question has a verified solution.

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

Well, all of us have seen the multiple EXCEL.EXE's in task manager that won't die even if you call the .close, .dispose methods. Try this method to kill any excels in memory. You can copy the kill function to create a check function and replace the …
If you need to start windows update installation remotely or as a scheduled task you will find this very helpful.
This lesson discusses how to use a Mainform + Subforms in Microsoft Access to find and enter data for payments on orders. The sample data comes from a custom shop that builds and sells movable storage structures that are delivered to your property. …
Look below the covers at a subform control , and the form that is inside it. Explore properties and see how easy it is to aggregate, get statistics, and synchronize results for your data. A Microsoft Access subform is used to show relevant calcul…
Suggested Courses

872 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