Restricting Access to Specific Columns

Unlike GRANT, the REVOKE statement has no syntax to specify privileges on a subset of columns in a table. To revoke the Select, Update, or References privilege on a column from a user, you must revoke the privilege for all the columns of the table. To provide access to some of the columns on which you previously had granted privileges, issue a new GRANT statement to restore the appropriate privilege on specific columns.

The next example cancels Select privileges for PUBLIC on certain columns: 
REVOKE SELECT ON customer FROM PUBLIC;
GRANT SELECT (fname, lname, company, city) ON customer TO PUBLIC;
In the next example, mary first receives the ability to reference four columns in customer, then the table owner restricts references to two columns: 
GRANT REFERENCES (fname, lname, company, city) ON customer TO mary;
REVOKE REFERENCES ON customer FROM mary;
GRANT REFERENCES (company, city) ON customer TO mary;