Question about locking order during merge statement

Dear all.
I have a merge query with a decedent hint to prevent deadlock with another queries.
Another queries use select ~for update with same hint.
My question is that the locking order will follow the hint in this query?
Or I might use the select ~ for update before this merege.
Please give any advice about select ~for update and locking order in the query.
Thanks.
MERGE INTO A
USING
     (SELECT /*+ index_desc(C index_key) */ *
     FROM
         C
      WHERE key > :start and key < :end
    ) B
     ON ( A.KEY = B.KEY )
WHEN MATCHED THEN
     UPDATE
     SET A.v1 = B.v1

What you are doing is not going to prevent a deadlock in your, as yet, unknown version of Oracle. Reading an index does not cause deadlocks. Trying to alter an uncommitted row does.
I would suggest you code this correctly by doing a SELECT FOR UPDATE WAIT <seconds> in all transactions.
http://www.morganslibrary.org/reference/deadlocks.html#dlfu

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Hi,
leave_for wrote:
HI,
I have question about dml mechanism. particularly delete statement
I learned that SQL statements deal with each row. I'm not sure what you mean.
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if so, Do DELETE statements deal with each row which is matched with terms WHERE statements? ortherwise with rownum?
I hope that I know the mechanism of DELETE statement?Sorry; the last couple of lines you wrote are especially confusing.
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