?
Solved

Table['Field'] vs Table.FieldByName('Field')

Posted on 1997-10-15
2
Medium Priority
?
624 Views
Last Modified: 2010-04-03
What is the difference between

Table['Field']
AND
Table.FieldByName('Field')

I was under the impression that the two methods both returned the same and that the first was quick-to-type
version of the second.

However in my program

 str := folders.fieldByName('name').AsString;

Works fine but
     
str := folders.['name'].AsString;

Genrates an exception.

Does anybody know why and how to use Table['field'] safely?
I cannot find it in the on-line help.
0
Comment
Question by:essbb
[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
2 Comments
 
LVL 5

Accepted Solution

by:
JimBob091197 earned 200 total points
ID: 1347614
Normally the 2 methods are interchangable.  However, if the field being returned is empty (i.e. null) then you cannot assign it to a string, as in "s := MyTable['MyField']".  You get an exception because you are trying to assign a null variant to a string type.

I.e. using the "MyTable['MyField']" method returns a variant, which can be null.  But, using the "MyTable.FieldByName('MyField').AsString" function will always return a string.  If the field is null, then the AsString function will return an empty string.

You could do the following, but you will end up typing more code anyway:
if (VarIsNull(MyTable['MyField'])) then
    s := ''
else
    s := MyTable['MyField'];

Normally, I only use the "MyTable['MyField']" method when assigning a value to the field.  When I read a value FROM the field, I use the AsString or AsInteger functions if there's a possibility of the return value being null.

Hope this is what you were looking for.
JB
0
 

Author Comment

by:essbb
ID: 1347615
JimBob,

Yes That seems to be the problem! I shouldn't be getting any Null
fields with my DB setup but it appears that I am. At least I know what bug(in my program) I am looking for now!

Thanks for your help
-Brett
0

Featured Post

What does it mean to be "Always On"?

Is your cloud always on? With an Always On cloud you won't have to worry about downtime for maintenance or software application code updates, ensuring that your bottom line isn't affected.

Question has a verified solution.

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

Objective: - This article will help user in how to convert their numeric value become words. How to use 1. You can copy this code in your Unit as function 2. than you can perform your function by type this code The Code   (CODE) The Im…
In this tutorial I will show you how to use the Windows Speech API in Delphi. I will only cover basic functions such as text to speech and controlling the speed of the speech. SAPI Installation First you need to install the SAPI type library, th…
Have you created a query with information for a calendar? ... and then, abra-cadabra, the calendar is done?! I am going to show you how to make that happen. Visualize your data!  ... really see it To use the code to create a calendar from a q…
In this video, Percona Solution Engineer Rick Golba discuss how (and why) you implement high availability in a database environment. To discuss how Percona Consulting can help with your design and architecture needs for your database and infrastr…
Suggested Courses
Course of the Month15 days, 8 hours left to enroll

741 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