Granting Access to Columns in a Table
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In addition to assigning access rights for an entire table, GRANT can assign UPDATE or REFERENCES privileges for certain columns of a table or view. To specify the columns, place the comma-separated list of columns in parentheses following the privileges to be granted in the GRANT statement.
The following statement assigns UPDATE access to all users for the CONTACT and PHONE columns in the CUSTOMERS table:
GRANT UPDATE (CONTACT, PHONE) ON CUSTOMERS TO PUBLIC;
You can add to the rights already assigned to users at the table level, but you cannot subtract from them. To restrict user access to a table, use the REVOKE statement.