INSERT INTO MasterList
(ComputerName, AuditId, IAV, Date)
SELECT
	t.ComputerName,
	t.AuditID,
	t.IAV,
	t.Date
FROM
	Temp t
	LEFT JOIN MasterList m
		ON m.ComputerName = t.ComputerName
WHERE
	m.ComputerName IS NULL;
	
	
INSERT INTO MasterList
(ComputerName, AuditId, IAV, Date)
SELECT
	t.ComputerName,
	t.AuditID,
	t.IAV,
	t.Date
FROM
	Temp t
WHERE NOT EXISTS
( SELECT * FROM MasterList m
  WHERE m.ComputerName = t.ComputerName);