Column-Level Security

Grant or revoke SELECT privileges to columns in a table. These privileges can be managed separately of table-level privileges, allowing for SELECT operations on a subset of columns.

• Column privileges are only enabled for tables.

• Column privileges other than SELECT such as UPDATE, DELETE are currently unsupported.

• Column-level security is not supported on queries that use one or more views.

Synopsis

GRANT SELECT (<column1>,<column2>,...<columnN>) ON TABLE <table> TO <entity>;

REVOKE SELECT (<column1>,<column2>,...<columnN>) ON TABLE <table> FROM <entity>;

The <entity> referred to above can either be a role or user.

The above GRANT and REVOKE commands can be compounded with other privileges. For example

GRANT SELECT (salary), UPDATE ON TABLE employees TO test_user;

grants the SELECT column privilege on the table employees to test_user as well as UPDATE privileges.

When using UPDATE or DELETE on a table, any columns used in the WHERE condition must allow for SELECT. That is, the entity issuing the command must have sufficient SELECT privileges to all columns in use. For example, SELECT privilege on the table being operated on is sufficient.

Currently, when a query utilizes a view, column-level privileges are disabled. In such cases, only table-level privileges are considered. Consequently, queries that might have adequate column-level privileges but also involve a view will result in an insufficient privileges error.

Examples

CREATE USER test_user (PASSWORD='test');
CREATE TABLE employees (id INT, salary BIGINT);

1. Grant SELECT on a single column.

GRANT SELECT(id) ON TABLE employees TO test_user;

1. Revoke SELECT on a single column.

REVOKE SELECT(id) ON TABLE employees FROM test_user;

The following also revokes column privileges.

REVOKE ALL ON TABLE employees FROM test_user;

1. Grant SELECT on multiple columns.

GRANT SELECT (id,salary) ON TABLE employees TO test_user;

1. Revoke SELECT on multiple columns.

REVOKE SELECT (id,salary) ON TABLE employees FROM test_user;

1. Granting SELECT on any column allows access to metadata.

-- Without privilege, the following exception will occur for test_user.
-- "Violation of access privileges: user test_user has no proper privileges for object employees"
SELECT count(*) FROM employees;

-- The following is run as an super-user or administrator. 
GRANT SELECT(id) ON TABLE employees TO test_user;
-- The following works without issue for test_user.
SELECT count(*) FROM employees; 

1. Allowing SELECT privilege on a subset of columns will enable certain queries and disable others.

-- The following is run as an super-user or administrator.
GRANT SELECT(id) ON TABLE employees TO test_user;

-- The following query completes without error for test_user.
SELECT id FROM employees;
-- The following query does not complete and reports no proper privileges for test_user.
SELECT id, salary FROM employees;

1. Any subqueries used within a query will enforce similar column-level security.

-- The following query completes without error for test_user.
SELECT * FROM (SELECT id FROM employees);

-- The following query does not complete and reports no proper privileges for test_user.
SELECT * FROM (SELECT id, salary FROM employees);

1. Table-level privileges supersede column-level privileges. Revoking column-privilege will not affect table-level privileges.

-- The following is run as an super-user or administrator.
GRANT SELECT ON TABLE employees TO test_user;
GRANT SELECT(id) ON TABLE employees TO test_user;

-- The following query completes without error for test_user.
SELECT id FROM employees;
-- The following query completes without error for test_user.
SELECT id, salary FROM employees;

-- The following is run as an super-user or administrator.
REVOKE SELECT(id) ON TABLE employees FROM test_user;
-- The following query completes without error for test_user. The user still has table-level privileges.
SELECT id, salary FROM employees;