Does Index get updated ??

Hello All,
 I have a question on index update..

There is a table (say A) with 10 columns and a unique index (say column loan_key)
An informatica job updates this table with a where clause of loan_key. The job also updates loan_key column even though the value does not change. So at an oracle level i see

update a
set loan_key = 123,
b = bbb
c = ccc
where loan_key = 123

will this update statement also cause the index to be updated even though the column value does not change.

Thank You,

Sat

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