Du kan gøre det ved at bruge enten:
ORDER BY FIND_IN_SET(id, '3,11,7,1')
eller
ORDER BY FIELD(id, 3, 11, 7, 1)
eller
ORDER BY CASE id WHEN 3 THEN 0
WHEN 11 THEN 1
WHEN 7 THEN 2
WHEN 1 THEN 3
ELSE 4
END