[AccessD] Why Change Field Size/was Change Field Size

Jürgen Welz jwelz at hotmail.com
Mon Dec 5 12:54:34 CST 2005


In Drew's case, this is not necessarily an issue as he has a demonstrated 
propensity not to use bound controls.

Queries, and particularly update or insert queries do not fail because of a 
field size limit any differently than in subseqent versions of Access.  They 
fail because users will use things like phone number fields that are limited 
to 255 characters to hold a dozen phone numbers and include descriptions 
such as 'His wife's vacation phone number for January 2006 - 1 900 555 5555' 
and they do this in a sufficent number of fields that the record page size 
limit is exceeded.

Data validation that includes record size limit restrictions at the user 
interface should preempt such problems.

Pop quiz, if you have a table that permits two date fields, indexed, 3 
longs, 2 indexed a boolean field, a memo field and 22 text fields, 2 
indexed, how many characters can you store in all 22 text fields before you 
can't save the record?  What if 3 of the text fields are indexed?  Clue, you 
used to get fewer characters in total as more are in indexed fields and I 
haven't bothered refiguring as our BE version changed in the rather foolish 
hope that MS didn't make this worse.  Oh, and give it a try with unicode.  
You'll need to know these things if you are doing record size validation.


Ciao
Jürgen Welz
Edmonton, Alberta
jwelz at hotmail.com





>From: "Charlotte Foust" <cfoust at infostatsystems.com>
>
>I've had queries go belly up because every field was 255, but that was
>in 97.  This is one of those issues that has caused a great deal of
>"discussion" in the list, so you can check the archives to see the
>arguments pro and con.  If you design a field to hold a specific value
>size, then your controls will limit the value for you with less work by
>the programmer.  If you allow them to enter 255 characters into a field
>that is only supposed to contain a social security number, then you have
>to do extra programming to make sure that all you get is a social
>security number.  I suppose my objection to making them all maximum
>length is that it's sloppy programming and suggests that you haven't
>really thought out the design of the table.
>
>Charlotte Foust





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