mssqlconn

From Free Pascal wiki
Jump to: navigation, search

English (en) español (es) français (fr)

Database portal

References:

Tutorials/practical articles:

Databases

Advantage - MySQL - MSSQL - Postgres - Interbase - Firebird - Oracle - ODBC - Paradox - SQLite - dBASE - MS Access - Zeos

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.

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.

Output parameters of stored procedures

Also, TMSSQLConnection and TSybaseConnection do not support handling of return status and output parameters of stored procedures. For more informations see: http://www.freetds.org/faq.html#ms.output.parameters 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"
  • Check if TCP port 1433 is opened
  • If you connect to specific instance of SQL Server (this is also case of SQL Server Express), check if SQL Server Browser Service is running on server (service listens on UDP port 1434)

Error 20019 : Attempt to initiate a new Adaptive Server operation with results pending

Error 20047 : DBPROCESS is dead or not enabled

  • SQL Server periodically verifies (by default every 30 seconds) if idle TCP/IP connection is still intact by sending a keep alive packet to its peer. If the remote system is still reachable and functioning, a acknowledge packet is sent back. If not local TCP will reset connection.
  • Adjust SQL Server Configuration Manager -> SQL Server Network Configuration -> Protocols -> TCP/IP : "Keep Alive"

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 depends on
  • 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;