Updating column by removing trailing spaces where column has a not null constraint

I have a table named documents where it has a column document_nbr  that has a not null constraint.
I want to remove any trailing spaces that are within the document_nbr's.

I have tried different combinations of an update statement but none seem to work, as it violates the not null constraint.
update documents
set document_nbr = trim(document_nbr)

Is there a way to update these columns while still having the not null constraint still being enabled?

I don't want to alter the table or create a temp table and add the records and reinsert them in or any type
of DDL command.

Is there a way to do this just by using an update statement?

Oracle 11g is used.

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slightwv (䄆 Netminder) Commented:
What value do you want the 'null' values set to?  If the column has all spaces and the not null constraint, it has to contain some value.

Maybe a junk character like '~':
update documents
set document_nbr = nvl(trim(document_nbr),'~')
MachinegunnerAuthor Commented:
Thanks for the reply.
I did try something like this earlier but it didn't work.
update documents
set document_nbr = nvl(rtrim(document_nbr), ' ')

When I try your update, I'm getting a violation key constraint now, so this column
is part of a key...

What do you think if I create a pl/sql procedure that has a cursor to go thru each record
and see if there are any spaces within, then try and update then in a loop?
That way I can add some conditions to check before the updates within the loop.

slightwv (䄆 Netminder) Commented:
What conditions would you add in a cursor loop?

What problem are you trying to solve?

If it is just to remove trailing spaces on rows that aren't ALL spaces then:
update documents
set document_nbr = trim(document_nbr)
where trim(document_nbr) is not null

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MachinegunnerAuthor Commented:
Thanks for the reply,
I tried the update statement and that didn't work.
I believe I was mentioning that I would create exception statement(s) to pass thru records
that instigate the constraints or ignore them.

More thinking about it, if I am removing the spaces and the document_nbr is part of a key,
this would mean that there are document_nbrs already in the system that are <blank> or
have empty spaces already.

So I would need to find these first maybe and see if there are any.
Thinking of trying this statement first and then if there are any records, then fix these first and then
run your update statement above.
Thanks for the help!

Select *
from documents
where nvl(trim(document_nbr), '~') = '~';
MachinegunnerAuthor Commented:
Tried this update statement as the best solution.
I need to clean up some records first then run the dml statement.
Thanks again!
slightwv (䄆 Netminder) Commented:
Glad to help!  We've all had to deal with 'bad' data...  ;)
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