SELECT
 (T_SAL.MatriculeSalarie || ' ' || NVL(T_SAL.Nom, ' ') || ' '  || NVL(T_SAL.Prenom, ' ') ) as Col1,
 'Date d''embauche : ' || TO_CHAR(T_HST_INFOSSOCIETE.DateEmbauche) 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 (     extract(MONTH FROM T_HST_INFOSSOCIETE.DateEmbauche ) = T_PAI.MoisEnCours
         and extract(YEAR FROM T_HST_INFOSSOCIETE.DateEmbauche ) = T_PAI.AnneeEnCours)

Order by T_SAL.MatriculeSalarie