Re: Mass updates to production tables (NULL to non-NULL)

You may have to worry about chaining.

NULL columns use no space, even when
they are CHAR() types.

If you are planning a counted cursor loop, don't. You can update by rowid ranges (the slightly harder way) but one simple option is:

    update tableX
    set col_name = ' '
    where col_name is null
    and rownum <= 10000;

    repeat until rows updated < 10,000

Regards

Jonathan Lewis
http://www.jlcomp.demon.co.uk

Next Seminar dates:
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The Co-operative Oracle Users' FAQ
http://www.jlcomp.demon.co.uk/faq/ind_faq.html

-----Original Message-----
To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com> Date: 25 November 2002 21:37

>I've got a real hot project (8.1.7.2 on HP/UX 11.0) that needs to
have NULLs
>converted to spaces on three different columns. Each is a CHAR, so I
>shouldn't need to worry about chaining, since that column's full size
has
>already been allocated in the block, right? But the first column has
1.2M
>NULLs out of 1.45M rows.
>
>My first test was to just UPDATE mytable SET mycol = ' ' WHERE mycol
IS
>NULL, after removing the index on that column. Seeing as there were
many
>more rows updated than I had anticipated, I was going to test the
UPDATE
>using a cursor, and committing at every 10K rows (~120 total commits)
to
>reduce rollback and locking issues.
>
>Thoughts? Since this table is used for time-and-attendance and
directly
>affects payroll, downtime isn't possible.
>
>TIA!
>
>Rich
>
>
>Rich Jesse System/Database Administrator
>Rich.Jesse_at_qtiworld.com Quad/Tech International, Sussex,
WI USA
>--
>Please see the official ORACLE-L FAQ: http://www.orafaq.com
>--
>Author: Jesse, Rich
> INET: Rich.Jesse_at_qtiworld.com
>
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-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.com
-- 
Author: Jonathan Lewis
  INET: jonathan_at_jlcomp.demon.co.uk

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