Assign + AddField = Problem

_Dejan_ · Post by **_Dejan_** » Mon 28 Dec 2009 07:48

Hi,
I have little problem. I using latest SDAC 4.80.0.54 and have little problem with VirtualTable component.
for example I would like fill data from TMSQuery to TVirtualtable but I get error.

Code: Select all

VirtualTable1.Assign(q_temp);
VirtualTable1.AddField('checked', ftBoolean, 0);

Im also try:

Code: Select all

VirtualTable1.Assign(q_temp);
VirtualTable1.Close;
VirtualTable1.AddField('checked', ftBoolean, 0);
VirtualTable1.Open;

and get same error.
Error:

Debug Output: [28.12.2009 8:36:02] Exception: Field 'ID' cannot be modified\0Dh Process Test.exe (2876)

Table structure in SQL Server:

Code: Select all

TABLE_CATALOG     COLUMN_NAME    COLUMN_DEFAULT DATA_TYPE CHARACTER_MAXIMUM_LENGTH 
----------------- -------------- -------------- --------- ------------------------ 
gps_new           ID             1              No        
gps_new           DESCRIPTION    2              YES       50
gps_new           GPS_ID         3              YES       20

What I would like to do? Have some "virtual table/query" which have data from sql server but with aditional column with name "checked" type = ftboolean.
Thanks for any help.

Plash · Post by **Plash** » Wed 30 Dec 2009 08:06

We could not reproduce the problem. Please send to support*devart*com a complete small sample that demonstrates the problem, including the script for creating database objects.

_Dejan_ · Post by **_Dejan_** » Thu 31 Dec 2009 07:21

Yesterday Im send example to email. Did you receive it?

Plash · Post by **Plash** » Thu 31 Dec 2009 12:27

Set the ReadOnly property of TMSQuery to False. The identity field is read-only anyway.

You need to remove a read-only attribute from the field before adding a new field:

Code: Select all

  VirtualTable1.Assign(q_zacasni);
  VirtualTable1.Close;
  VirtualTable1.FieldDefs[0].Attributes :=
    VirtualTable1.FieldDefs[0].Attributes - [faReadOnly];
  VirtualTable1.AddField('checked', ftBoolean, 0);

_Dejan_ · Post by **_Dejan_** » Thu 31 Dec 2009 19:43

Hi thanks for this info. Now it works.
Im do:

Code: Select all

q_zacasni.ReadOnly:=False;
VirtualTable1.Assign(q_zacasni);
VirtualTable1.AddField('checked', ftBoolean, 0);

And it works. Thanks.

_Dejan_ · Post by **_Dejan_** » Fri 21 Oct 2011 11:14

I would like wake up this thread.
When Im try run another query Im start receiving errors:

Code: Select all

First chance exception at $7C812AFB. Exception class EDatabaseError with message 'Field 'field1' cannot be modified'. Process App.exe (200)

Code:

Code: Select all

procedure TForm1.FormCreate(Sender: TObject);
var q_temp :TMSQuery;
begin
 try
  q_temp:=TMSQuery.Create(Self);
  q_temp.Connection:=DataModule1.Connection;
  q_temp.ReadOnly:=False;
  q_temp.SQL.Clear;
  q_temp.SQL.Add('SELECT DISTINCT t.field1, (SELECT table1.field2 + ' + QuotedStr(', ') + ' AS [text()] FROM table1 WHERE table1.field1 = t.field1 ORDER BY table1.field2 FOR XML Path(' + QuotedStr('') + ')) AS field3 FROM table1 t');
  q_temp.Open;

  VirtualTable1.Assign(q_temp);
  VirtualTable1.Close;
  VirtualTable1.FieldDefs[0].Attributes:=VirtualTable1.FieldDefs[0].Attributes - [faReadOnly];
  VirtualTable1.AddField('checked', ftBoolean, 0);
  VirtualTable1.Open;
 finally
  q_temp.Close;
  q_temp.Free;
 end;
end;

any hint?

AndreyZ · Post by **AndreyZ** » Tue 25 Oct 2011 14:17

I cannot reproduce the problem. Your code works without any errors. Please specify the exact moment when the 'Field 'field1' cannot be modified' occurs.