Incearca:

DECLARE @tmp TABLE(id tinyint IDENTITY(1, 1), col1 varchar(10))
INSERT INTO @tmp VALUES('a')
INSERT INTO @tmp VALUES('b')
INSERT INTO @tmp VALUES('c')
INSERT INTO @tmp VALUES('d')............etc......

 UPDATE Table1 SET c3 = NULL, c4 = tmp.col1
FROM Table1 t1 JOIN @tmp tmp ON t1.id = tmp.id

*Table1 este tabelul  (id, c1, c2, c3, c4)