Update after a table field change - sql-server

Question

I have a problem with a old Delphi system, this system insert data into a SQL Server table.
After 10 years change a field of the table from 100 to 255 chars long.
The system select all the registris of the table, and put them on an other table after a transformation. That works fine.
The problems are when the system update a field.
That show me the error
EDBEngineError with message 'Couldn't perform the edit because another user changed the record.
sConsulta:='SELECT * FROM cuentas WHERE (WALL= 2) AND (SEND_DATE = '01/01/1970')';
m_oQryLeg.Close;
m_oQryLeg.SQL.Clear;
m_oQryLeg.SQL.Add(sConsulta);
m_oQryLeg.Open;
m_oTblNov.Close;
m_oTblNov.TableName:='des_table';
m_oTblNov.Open;
with m_oTblNov do
begin
while (not m_oQryLeg.EOF) do
begin
Insert;
FieldbyName('COD_HOME').AsString:= m_oQryLeg.FieldByName('USR_HOME').AsString;
(...)
Post;
m_oQryLeg.Edit;
m_oQryLeg.FieldByName('SEND_DATE').AsDateTime:= Date; //<-- HERE THE ERROR
m_oQryLeg.Post;
m_oQryLeg.First;
m_oQryLeg.MoveBy(i);
inc(i);
end;
end;
m_oTblNov.Close;
m_oQryLeg.Close;
UpdateMode: upWhereAll
cuentas table:
NUM_SOL nvarchar 6 *PK
WALL tinyint 1
SEND_DATE smalldatetime 4
OBS_CRED nvarchar 255
FLCC real 4
STREET nvarchar 30

Answer 1

You're trying to update a query you're using on a table you're editing at the same time, and it's not going to work.
Since you know you're going to insert every row from the query into m_oTblNov, why not just do it like this instead?
sConsultaSELECT :='SELECT * FROM cuentas';
sConsultaUPDATE := 'UPDATE cuentas SET Send_Date = :New_Date';
// Separate WHERE so you can use it twice. Note the leading space
// between the first ' and WHERE.
sWhere := ' WHERE (WALL = 2) and (SEND_DATE = ''01/01/1970'')';
m_oQryLeg.Close;
m_oQryLeg.SQL.Text := sConsulta + sWhere;
m_oQryLeg.Open;
m_oTblNov.Close;
m_oTblNov.TableName:='des_table';
m_oTblNov.Open;
with m_oTblNov do
begin
while (not m_oQryLeg.EOF) do
begin
Insert;
FieldbyName('COD_HOME').AsString:= m_oQryLeg.FieldByName('USR_HOME').AsString;
(...)
Post;
// Don't run these any more. See below.
// m_oQryLeg.Edit;
// m_oQryLeg.FieldByName('SEND_DATE').AsDateTime:= Date; //<-- HERE THE ERROR
// m_oQryLeg.Post;
m_oQryLeg.First;
m_oQryLeg.MoveBy(i);
inc(i);
end;
end;
m_oTblNov.Close;
m_oQryLeg.Close;
m_oQryLeg.SQL.Text := sConsultaUPDATE + sWHERE;
m_oQryLeg.ParamByName('New_Date').AsDateTime := Date;
try
m_oQryLeg.ExecSQL;
finally
m_oQryLeg.Close;
end;

Answer 2

The problem here is that your object is trying to refresh the row from the database to make sure nothing has changed and more than likely the object truncated or rounded some value that is causing the refresh to return no rows.
This could be caused by either a float value being truncated or some other value being off.
if you don't/can't change that column to fix this issue I would advise changing to either upWhereChanged or upWhereKeyOnly.
Given that dates are treated as doubles in most windows databases, I would think that upWhereKeyOnly would be best.
EDIT:
After looking at your table, it may have to do with the fact you are using a single based smalldatetime. Delphi treats all DateTime data as a double and the conversion back and forth may be causing small rounding issues.