Using MERGE in SQL Server 2008 - sql-server-2008

Question

I just found out about this nifty little feature. I have a couple questions. consider the statement below.
This is how interpret how it works. The USING statement is what gets compared to see if there is a match correct? I want to use how it is now, but I want to use 2 other columns from the source table in the MATCH portion. I can't do that. So is there a way that I can use the 2 columns (decesed (I know its spelled wrong :) ) and hicno_enc)?
Another thing I would like to do and don't know if it possible, but if the row exists in target but not source, then mark it inactive.
SELECT FIRST_NAME, LAST_NAME, SEX1, BIRTH_DATE
FROM
aco.tmpimport i
INNER JOIN aco.patients p
ON p.hicnoenc = i.hicno_enc
MERGE aco.patients AS target
USING (
SELECT FIRST_NAME, LAST_NAME, SEX1, BIRTH_DATE
FROM aco.tmpimport
) AS source
ON target.hicnoenc = source.hicno_enc
WHEN MATCHED AND target.isdeceased <> CONVERT(BIT,source.decesed) THEN
UPDATE
SET
target.isdeceased = source.decesed,
updatedat = getdate(),
updatedby = 0
WHEN NOT MATCHED THEN
INSERT (firstname, lastname, gender, dob, isdeceased, hicnoenc)
VALUES (source.FIRST_NAME,
source.LAST_NAME,
source.sex1,
source.BIRTH_DATE,
source.decesed,
source.hicno_enc);

Answer 1

So is there a way that I can use the 2 columns (decesed (I know its
spelled wrong :) ) and hicno_enc)?
Add the columns you need in the select statement in the using clause.
USING (
SELECT FIRST_NAME, LAST_NAME, SEX1, BIRTH_DATE, decesed, hicno_enc
FROM aco.tmpimport
) AS source
if the row exists in target but not source, then mark it inactive.
Add a when not matched by source clause and do the update.
WHEN NOT MATCHED BY SOURCE THEN
UPDATE
SET active = 0