I have a table abc and I have applied a policy for update. Now the user who has no access is unable to update the table abc. Can I just restrict the user from updating a specific column ( user_id column in the table abc), rather than restricting the user from updating all columns?
You can also use views to enforce column-level security, showing only which columns in a table may be updated. For example, assume that you must design roles based a table where only managers may view or update the salary column of the employee table (column restriction).
1 - You can grant the end-user access to only those columns you wish to update:
grant update (col1, col2) on mytab to fred;
2 - You might create a view with only those columns that you want to allow updates, the table appears to the end-user as-if it contains only those columns. By granting access only to that view (and not the base table), you can effectively implement column-level security and restrict which columns in a table may be changed.