mssqlconn

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Revision as of 07:23, 3 March 2015 by Lacak (talk | contribs)

Overview

mssqlconn is an fcl-db unit containing connector code for TMSSQLConnection (MS SQL Server) and TSybaseConnection (Sybase ASE).

Lazarus uses mssqlconn to present an MS SQL connector and Sybase ASE connector.

sqldbcomponents.png

DBLib

mssqlconn uses the dblib low-level unit which requires the FreeTDS library (.dll/.dylib/.so) to connect to the server.

Installation

The only thing you need is a FreeTDS dll/dylib/so for your platform.

  • On Linux, download the freetds package which provides libsybdb.so (e.g. in Debian this is provided by package libsybdb5) and the related development package using your package manager. You might also need to add a symbolic link libsybdb.so to libsybdb.so.5
  • On Windows, you can download a recent 32 or 64 bit version of the FreeTDS library dblib.dll here: [1]

Advanced use: by modifying FPC file dblib.pas SQLDB could use the "native" library ntwdblib.dll instead of the default FreeTDS library dblib.dll (in this case FPC needs to be recompiled).

Documentation

Official documentation: FPC documentation on mssqlconn

Limitations and tips

  • Sybase port: the default port for Sybase ASE is 5000. As FreeTDS/mssqlconn uses 1433 by default, you may want to add :5000 to the hostname proprerty automatically or after feedback from the end user.

As the documentation specifies:

  • you might need to tweak some parameters for BLOB support.
  • MS SQL multiple resultsets (MARS) are not supported.

Also, TMSSQLConnection and TSybaseConnection do not support handling of return status and output parameters of stored procedures. As a workaround you can use something like:

with SQLQuery1 do begin
  SQL.Text:='declare @param int; declare @ret int;'+
            'exec @ret=MyStoredProc 1, @param OUTPUT;'+
            'select @ret as return_status, @param as out_param';
  Open;
end;

Some more tips:

Error messages

=== Error 20009 : Unable to connect: Adaptive Server is unavailable or does not exist===

  • Check if TCP/IP protocol is enabled on SQL Server side using "SQL Server Configuration Manager" - "SQL Server Network Configuration"

EINOutError/Can not load DB-Lib client library "dblib.dll". Check your installation

  • Make sure you have all required dlls installed (e.g. dblib.dll, libiconv2.dll)
  • Make sure you have all required C/C++ runtime libraries installed that dblib.dll
  • Make sure the bitness (32 or 64 bit) of the dblib library and your compiled program match

Examples

Creating a database

The example below creates a database on an MS SQL Server. For this to work, the connection's parameter AutoCommit must be set to on. For normal subsequent connection you can switch it off again and use regular StartTransaction and Commit.

// Set up a form with a button called DBButton, 
// textbox called DatabaseNameEdit,
// '''MSSQLConnection''' called FConn
// ***make sure the Autocommit parameter is on for the create db part before connectiong:
//FConn.Params.Add('AutoCommit=true');
procedure TForm1.CreateDBButtonClick(Sender: TObject);
var
  CurrentDB: string;
begin
  if DatabaseNameEdit.Text='' then
  begin
    showmessage('Empty database name. Please specify database name first.');
    exit;
  end;

  CurrentDB:=FConn.DatabaseName;
  try
    // For FPC 2.6.1+
    FConn.ExecuteDirect('CREATE DATABASE '+DatabaseNameEdit.Text);
    {
    // This works with FPC 2.7.1, not on 2.6.1
    FConn.CreateDB;
    }
  except
    on E: Exception do
    begin
      showmessage('Exception running CreateDB: '+E.Message);
    end;
  end;
end;



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