Dont allow updation for few columns in a record. - Mailing list pgsql-novice

Hi all,
    Is it possible to say that once a record is inserted into the
table, nobody can update some particular columns in that record.

(eg)
table
------
prod_id prod_name prod_desc
  1      name1      desc1
  2      name2      desc2

In this table i dont want to allow updation of the prod_name column.

I can write a trigger to do this job, but is there any way to specify
during the table creation time itself that these columns cannot be
altered.


TIA
--
regards,
hari
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