Does praying Tahiyyat al-Masjid mean that one
    does not have to pray Sunnat al-Fajr?
Question

                If a person enters the mosque
      and prays Tahiyyat al-Masjid, does that mean that he does not need to pray the two
      Rak’ahs of Sunnat al-Fajr? Or should he pray Tahiyyat al-Masjid and then do the two
      Rak’ahs of Sunnat al-Fajr?
Praise be to Allah.If he enters the mosque and prays Sunnat
    al-Fajr, this is sufficient and he does not have to pray Tahiyyat al-Masjid. If he makes
    the intention of praying both, then that is fine.
And Allaah is the source of strength. May Allaah bless our
    Prophet Muhammad and his family and companions.