when packing a dbf table, an error is file is in use - delphi

Question

When trying to make a request, it displays an error:
File is in use
How can I solve that program?
procedure TForm1.Button4Click(Sender: TObject);
var data,ffg:string;
begin
data:=formatdatetime('ddmm',(DateTimePicker1.Date));
Adoquery2.SQL.Clear;
adoquery2.SQL.text:='Delete from g_rabn where data=data';// deleting data from g_rabn
adoquery2.ExecSQL;
ShowMessage(SysErrorMessage(GetLastError));
end;
procedure TForm1.Button5Click(Sender: TObject);
begin
Adoquery3.close;
Adoquery3.SQL.Clear;
adoquery3.SQl.text:='pack table g_rabn';// packing tablr g_rabn
adoquery3.Open;
ShowMessage(SysErrorMessage(GetLastError));
end;
end.
I can not delete data from the table, they are marked as deleted but require packaging. How to do it programmatically? He writes that file is in use when packing what to do?

Answer 1

You should execute the statement, not open it as a query. One way to achieve that, is to run it using an TADOCommand, not an TADOQuery, or use the ExecSQL method of the TADOQuery.
Also, all other connections to the DBF must be closed, otherwise you can't get the exclusive access that you need for packing the table.
I found this thread from 2005 on another forum, where somebody made this work with two notable parameters:
Using the provider VFPOLEDB.1
Using just the command pack filename.dbf (without the table keyword).
Lastly, I'm not so sure about the line ShowMessage(SysErrorMessage(GetLastError));. This will show you the last API error, but that's on a low level. You are using the ADO components, so if anything is going wrong, you should expect ADO to throw an exception. For all you know ADO already worked around the issue one way or the other, and the error message you're seeing is not even relevant.

Answer 2

I am surprised that I could not get the solution suggested in Golez Troi's answer
to work, especially as it refers to a newsgroup post from someone who had seemingly managed to pack a dBASE table using ADO; as I said in a comment, if I try to call 'Pack xxxx' to pack a dBASE table via ADO, however I do it, I get
Invalid SQL Statement; DELETE, INSERT, PROCEDURE, SELECT or UPDATE expected
.
I was also surprised to notice something in the MS ODBC dBASE docs that I'd not noticed before, namely that the MS ODBC driver for dBASE files requires the BDE
Note
Accessing dBASE ISAM files through the ODBC Desktop Database Drivers requires installation of the Borland database engine
So, seeing as accessing dBASE files via Ado requires the BDE anyway, there seems to me to be
no point avoiding using the BDE to pack the dBASE table using the standard BDE method, namely to call DbiPackTable. I added a TDatabase and TTable
to my ADO test project, after which I was able to execute this code without any problem
procedure TForm1.Button2Click(Sender: TObject);
begin
try
// Insert code here to close any Ado object (TAdoConnection, TAdoCommand, etc) pointing
// at the dBASE table/file
// Also check that not Ado object pointing at it is open in the IDE
//
// Then ...
Database1.DatabaseName := 'MADBF2';
Database1.Connected := True;
Table1.TableName := 'MATest.Dbf';
Table1.Exclusive := True;
Table1.Open;
// Following uses a call to DbiPackTable to pack the target table
Check(DbiPackTable(Table1.DBHandle, Table1.Handle, nil, nil,True));
finally
Table1.Close;
Database1.Connected := False;
end;
end;
FWIW, while I was writing this answer, I noticed that the BDE.Int file (which gives the declarations but not the implementation of the BDE interface) was on the D7 distribution CD but was apparently not installed by default).