Difference between revisions of "Talk:Lazarus Database Overview"

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(removed obsolete stuff. If you want to update the code samples on the wiki, don't ask to do it, just do it ;))
 
(8 intermediate revisions by 4 users not shown)
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Hi,
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=== Splitting up so more organized? ===
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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).
  
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I would like to change some code given in the MySQL example for Lazarus. I think there are some fundamental errors here.
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Whatever remains will be perhaps a list of supported databases which can be merged with similar lists for FPC...
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For instance
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--[[User:BigChimp|BigChimp]] 06:26, 22 May 2012 (UTC)
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procedure ShowString (S : string);
 
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(* display a string in a Memo box *)
 
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begin
 
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        trymysqlForm1.ResultsMemo.Lines.Add (S)
 
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end;
 
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should be done in a methode of the form like:
 
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procedure TtrymysqlForm1.ShowString (S : string);
 
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(* display a string in a Memo box *)
 
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begin
 
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        ResultsMemo.Lines.Add (S)
 
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end;
 
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It makes the use of the trymysqlForm1 variable obsolete, which might be the cause of runtime errors.
 
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Well to cut a long story short, I would like the code to be changed into:
 
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procedure TFormTryMySQL.QueryButtonClick(Sender: TObject);
 
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var
 
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  tableBuffer: PMYSQL_RES;
 
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  recordBuffer: TMYSQL_ROW;
 
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  fieldList: TStringList;
 
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  I: Integer;
 
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  stMessage: String;
 
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begin
 
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  // Show how we can get records from a table
 
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  StatusBar1.SimpleText := 'Executing query: ' + CommandEdit.Text;
 
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  ShowString('Executing query: ' + CommandEdit.Text);
 
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  if (mysql_query(mySQLSock, PChar(CommandEdit.Text)) < 0) then begin
 
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    ShowString('Query failed '+ StrPas(mysql_error(mySQLSock)));
 
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  end else begin
 
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    tableBuffer := mysql_store_result(mySQLSock);
 
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    try
 
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      if tableBuffer = nil then begin
 
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        ShowString('Query didnot return any results.');
 
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      end else begin
 
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        fieldList := TStringList.Create;
 
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        try
 
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          ShowString('Number of records returned  : ' + IntToStr(mysql_num_rows(tableBuffer)));
 
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          ShowString('Number of fields per record : ' + IntToStr(mysql_num_fields(tableBuffer)));
 
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          // Lets get a list a returned fields.
 
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          for I := 0 to pred(mysql_num_fields(tableBuffer)) do begin
 
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            fieldList.Add(mysql_fetch_field_direct(tableBuffer, I).name);
 
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          end;
 
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          recordBuffer := mysql_fetch_row(tableBuffer);
 
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          while (recordBuffer <> nil) do begin
 
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            stMessage := '';
 
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            for I := 0 to pred(mysql_num_fields(tableBuffer)) do begin
 
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              stMessage := stMessage + fieldList[I] + ': ' + recordBuffer[I] + ', ';
 
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            end;
 
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            Delete(stMessage, Length(stMessage) - 2, 2);
 
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            ShowString(stMessage);
 
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            recordBuffer := mysql_fetch_row(tableBuffer);
 
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          end;
 
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        finally
 
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          fieldList.Free;
 
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        end;
 
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      end;
 
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    finally
 
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      // Free the results, thus saving resources.
 
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      mysql_free_result(tableBuffer);
 
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    end;
 
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  end;
 
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end;
 
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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.
 

Latest revision as of 12:51, 8 May 2014

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)

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