[SOLVED] TDBf Primary Fields
lazarus / 16-Databases

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1HuntnMan · 2024-02-05 20:50

Has anyone questioned why when adding the first record to a Dbf table
containing a AutoInc-primary field, that field's value is assigned 0
instead of 1?  This was a question I was asked by one of my users who
is testing this new app? I'm relatively new to programming. So, I went
into the system and in every table with a primary AutoInc primary
field I added a new record first, copied it to a new record and then
deleted the 0 record.  Now the 3 people testing this new app are
happier because there are no 0 records  !

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Zvoni · 2024-02-06 07:33

What's wrong with 0 for a (Primary Key?) Auto-Inc-Field?
It's a value you (and anyone else) shouldn't be interested in at all

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korba812 · 2024-02-06 11:41

Quote from: Zvoni on February 06, 2024, 08:33:23 amWhat's wrong with 0
for a (Primary Key?) Auto-Inc-Field?
It's a value you (and anyone else) shouldn't be interested in at all
In the case of DBF, this is important because standard numeric fields
do not know NULL value and the zero (0) value is used instead. Most
Auto-Inc implementations in DBF number from 1.

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Zvoni · 2024-02-06 14:31

Quote from: korba812 on February 06, 2024, 12:41:26 pmIn the case of
DBF, this is important because standard numeric fields do not know
NULL value and the zero (0) value is used instead. Most Auto-Inc
implementations in DBF number from 1.
OK. Accepted.
Didn't know that, since the last time i was in "contact" with dBase
was 1996 in economic school

EDIT: Found something in "...\source\packages\fcl-
db\src\dbase\dbf_dbffile.pas"
Line 854 (FPC3.2.2 - 32Bit)
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i  // Update
our field list      with FFieldDefs.AddFieldDef do      begin       
Assign(lFieldDef);        Offset := lFieldOffset;        AutoInc :=
0;      end;There.
AutoInc:=0;

and looking further through the file, any mention of "AutoInc" that
has a direct assignment, assigns "0", even "local" variables
containing "AutoInc" in its name

https://www.freepascal.org/daily/packages/fcl-
db/dbf_fields/tdbffielddef.html
As far as i understand it: If you create everything from FPC-Code, you
should be able to set AutoInc to whatever Startvalue you want (Don't
forget AutoIncStep) when you create the FieldDefs.

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1HuntnMan · 2024-02-11 21:34

I totally agree and understand that a Primary/AutoInc field starts
with 0. But, the users could give a flip. They just don't like a 0
Appointment ID. They want the Appointment No. to be a 1 and increment
from there. I guess I should have given them a true Appointment No./ID
field instead of using the Primary key. Would be easy to change...
Thanks