if exists (select 1 from Candidates where CandidateID in (select CandidateID from New_Candidates))
	begin
		update Candidates
		set col1 = col1
		where CandidateID in (select CandidateID from New_Candidates)
	end

if not exists (select 1 from Candidates where CandidateID in (select CandidateID from New_Candidates))
	begin
		insert into Candidates (CandidateID, col1)
		select CandidateID, col1 from New_Candidates
		where CandidateID not in (select CandidateID from Candidates)
	end

--No IF necessary - if they join up then it exists, otherwise it doesn't
update c set
	c.col = nc.col
from	Candidates c
join	new_Candidates nc
		on nc.CandidateID = c.CandidateID

--LEFT OUTER JOIN with WHERE ID is Null replaces the "if not exists (<select out the whole table>)"
insert Candidates (colList)
select colList
from	new_Candidates nc
left join Candidates c
		on c.candidateID = nc.candidateID
where	c.CandidateID is NULL