Talk:Lazarus Database Overview

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Splitting up so more organized?

This page used to be a tutorial but has changed to become an overview page of various databases and access mechanisms. I propose moving the database specific part out to their own pages (e.g. MySQL) and moving general SQLDB tutorials (e.g. the mysql code-driven example) to a new SQLDB tutorial page, but stripped of db specifics as far as possible (see SQLDB Tutorial1 for an example).

Whatever remains will be perhaps a list of supported databases which can be merged with similar lists for FPC... --BigChimp 06:26, 22 May 2012 (UTC)

Suggestions from 2005 - can these be removed?

Is this still relevant or does this need to be removed? --BigChimp 11:21, 8 August 2011 (CEST)

Hi,

I would like to change some code given in the MySQL example for Lazarus. I think there are some fundamental errors here. For instance

procedure ShowString (S : string);
(* display a string in a Memo box *)
begin
       trymysqlForm1.ResultsMemo.Lines.Add (S)
end;

should be done in a methode of the form like:

procedure TtrymysqlForm1.ShowString (S : string);
(* display a string in a Memo box *)
begin
       ResultsMemo.Lines.Add (S)
end;

It makes the use of the trymysqlForm1 variable obsolete, which might be the cause of runtime errors. Well to cut a long story short, I would like the code to be changed into:

procedure TFormTryMySQL.QueryButtonClick(Sender: TObject);
var
  tableBuffer: PMYSQL_RES;
  recordBuffer: TMYSQL_ROW;
  fieldList: TStringList;
  I: Integer;
  stMessage: String;
begin
  // Show how we can get records from a table
  StatusBar1.SimpleText := 'Executing query: ' + CommandEdit.Text;
  ShowString('Executing query: ' + CommandEdit.Text);
  if (mysql_query(mySQLSock, PChar(CommandEdit.Text)) < 0) then begin
    ShowString('Query failed '+ StrPas(mysql_error(mySQLSock)));
  end else begin
    tableBuffer := mysql_store_result(mySQLSock);
    try
      if tableBuffer = nil then begin
        ShowString('Query didnot return any results.');
      end else begin
        fieldList := TStringList.Create;
        try
          ShowString('Number of records returned  : ' + IntToStr(mysql_num_rows(tableBuffer)));
          ShowString('Number of fields per record : ' + IntToStr(mysql_num_fields(tableBuffer)));
          // Lets get a list a returned fields.
          for I := 0 to pred(mysql_num_fields(tableBuffer)) do begin
            fieldList.Add(mysql_fetch_field_direct(tableBuffer, I).name);
          end;
          recordBuffer := mysql_fetch_row(tableBuffer);
          while (recordBuffer <> nil) do begin
            stMessage := ;
            for I := 0 to pred(mysql_num_fields(tableBuffer)) do begin
              stMessage := stMessage + fieldList[I] + ': ' + recordBuffer[I] + ', ';
            end;
            Delete(stMessage, Length(stMessage) - 2, 2);
            ShowString(stMessage);
            recordBuffer := mysql_fetch_row(tableBuffer);
          end;
        finally
          fieldList.Free;
        end;
      end;
    finally
      // Free the results, thus saving resources.
      mysql_free_result(tableBuffer);
    end;
  end;
end;

There are some more changes, in fact I expanded it with a second form to show data in a ListView. So if there is any interest in that I'm willing to contribute it to the documentation project.

Matthijs

This page has been converted from the epikwiki version.


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