SELECT
 (T_SAL.MatriculeSalarie + ' ' + isnull(T_SAL.Nom, '') + ' '  + isnull(T_SAL.Prenom, '') ) as Clo1,
 'Date d''embauche : '+  CONVERT(VARCHAR(12),T_HST_INFOSSOCIETE.DateEmbauche, 113) as Col2
FROM
  T_PAI,
  T_SAL
  LEFT OUTER JOIN T_HST_INFOSSOCIETE ON T_HST_INFOSSOCIETE.NumSalarie=T_SAL.SA_CompteurNumero
                  AND T_HST_INFOSSOCIETE.InfoEnCours=1
Where  (T_HST_INFOSSOCIETE.DateEmbauche is null)
    or (     DatePart(mm, T_HST_INFOSSOCIETE.DateEmbauche) = T_PAI.MoisEnCours
         and DatePart(yyyy, T_HST_INFOSSOCIETE.DateEmbauche) = T_PAI.AnneeEnCours)

Order by T_SAL.MatriculeSalarie