PostgreSQL GRANT Statement

Summary: in this tutorial, you will learn how to use the PostgreSQL GRANT statement to grant privileges on database objects to a role.

Introduction to PostgreSQL GRANT statement

After creating a role with the LOGIN attribute, the role can log in to the PostgreSQL database server.

However, it cannot do anything to the database objects like tables, views, functions, etc. For example, the role cannot select data from a table or execute a specific function.

To allow a role to interact with database objects, you need to grant privileges on the database objects to the role using the GRANT statement.

The following shows the simple form of the GRANT statement that grants one or more privileges on a table to a role:

GRANT privilege_list | ALL
ON  table_name
TO  role_name;

In this syntax:

First, specify the privilege_list that can be SELECT, INSERT,UPDATE, DELETE,TRUNCATE, etc. Use the ALL option to grant all privileges on a table to the role.
Second, provide the name of the table after the ON keyword.
Third, indicate the name of the role to which you want to grant privileges.

PostgreSQL GRANT statement examples

First, use the postgres user to connect to the PostgreSQL server using any client tool of your choice, for example, psql:

psql -U postgres

Second, create a new user role called joe that can log in to the PostgreSQL server:

create role joe
login
password 'YourPassword';

Replace the YourPassword with the one you want.

Third, create a new table called candidates:

create table candidates (
    candidate_id int generated always as identity,
    first_name varchar(100) not null,
    last_name varchar(100) not null,
    email varchar(255) not null unique,
    phone varchar(25) not null,
    primary key(candidate_id)
);

Fourth, use the role joe to log in to the PostgreSQL server in a separate session.

Fifth, attempt to select data from the candidates table from the joe‘s session:

SELECT * FROM candidates;

PostgreSQL issued an error:

ERROR:  permission denied for table candidates

The output indicates that the role joe does not have the privilege of retrieving data from the candidates table.

To grant the SELECT privilege on the candidates table to the role joe, you execute the following GRANT statement in the postgres‘ session:

GRANT SELECT
ON candidates
TO joe;

Sixth, execute the SELECT statement from the joe‘s session:

SELECT * FROM candidates;

PostgreSQL returns an empty result set instead of an error.

Seventh, execute the following INSERT statement:

INSERT INTO candidates(first_name, last_name, email, phone)
VALUES('Joe','Com','[[email protected]](../cdn-cgi/l/email-protection.html)','408-111-2222');

PostgreSQL issued the following error because joe does not have the INSERT privilege on the candidates table:

ERROR:  permission denied for table candidates

Eighth, grant INSERT, UPDATE, and DELETE privileges on the candidates table to the role joe:

GRANT INSERT, UPDATE, DELETE
ON candidates
TO joe;

Ninth, execute the INSERT statement again from the joe‘s session:

INSERT INTO candidates(first_name, last_name, email, phone)
VALUES('Joe','Com','[[email protected]](../cdn-cgi/l/email-protection.html)','408-111-2222');

Now, joe can insert data into the candidates table. Additionally, it can update or delete data from the table.

More PostgreSQL GRANT statement examples

Let’s take some more examples of using the GRANT statement.

1) Grant all privileges on a table to a role

The following statement grants all privileges on the candidates table to the role joe:

GRANT ALL
ON candidates
TO joe;

2) Grant all privileges on all tables in a schema to a role

The following statement grants all privileges on all tables in the public schema of the dvdrental sample database to the role joe:

GRANT ALL
ON ALL TABLES
IN SCHEMA "public"
TO joe;

3) Grant SELECT on all tables

Sometimes, you want to create a readonly role that can only select data from all tables in a specified schema.

To do that, you can grant the SELECT privilege on all tables in the public schema like this:

GRANT SELECT
ON ALL TABLES
IN SCHEMA "public"
TO reader;

So far, you have learned how to grant privileges on tables. To grant privileges to a role on other database objects, check the GRANT statement syntax.

Summary

Use the GRANT statement to grant privileges on database objects to a role.

PostgreSQL GRANT