postgres list users and roles with code examples

PostgreSQL is an open-source relational database management system (RDBMS) that is widely used in web and enterprise applications. It has a rich set of features and is known for its stability and performance. One of the most important aspects of managing a PostgreSQL database is managing users and roles. In this article, we will discuss how to list users and roles in PostgreSQL, along with code examples.

Listing Users in PostgreSQL
To list all the users in a PostgreSQL database, you can use the following SQL query:

SELECT usename FROM pg_user;

This query will return a list of all the users in the database, including the default users that are created when PostgreSQL is installed.

Listing Roles in PostgreSQL
To list all the roles in a PostgreSQL database, you can use the following SQL query:

SELECT rolname FROM pg_roles;

This query will return a list of all the roles in the database, including the default roles that are created when PostgreSQL is installed.

Listing Users and Roles in PostgreSQL
To list both users and roles in a PostgreSQL database, you can use the following SQL query:

SELECT usename as name, 'user' as type FROM pg_user
UNION
SELECT rolname as name, 'role' as type FROM pg_roles;

This query will return a list of all the users and roles in the database, along with their type (user or role) in a single result set.

Listing roles of a specific user
To list all roles of a specific user, you can use the following SQL query:

SELECT rolname FROM pg_roles
WHERE oid IN (
  SELECT roleid FROM pg_auth_members
  WHERE member = (SELECT usesysid FROM pg_user WHERE usename='<username>')
);

This query will return a list of all the roles that are assigned to the specific user. Replace with the name of the user you want to query.

Listing users in a specific role
To list all users in a specific role, you can use the following SQL query:

SELECT usename FROM pg_user
WHERE usesysid IN (
  SELECT member FROM pg_auth_members
  WHERE roleid = (SELECT oid FROM pg_roles WHERE rolname='<rolename>')
);

This query will return a list of all the users that are assigned to the specific role. Replace with the name of the role you want to query.

In conclusion, managing users and roles in PostgreSQL is an important aspect of maintaining a secure and stable database. The above queries and examples provide a good starting point for listing users and roles in PostgreSQL. It is important to note that these queries should be executed by a user with sufficient privileges, such as a superuser or a user with the appropriate GRANTs.

Creating Users in PostgreSQL
To create a new user in PostgreSQL, you can use the CREATE USER SQL command. The basic syntax for creating a new user is as follows:

CREATE USER <username> [OPTIONS];

The options available for the CREATE USER command include:

• PASSWORD: sets the password for the new user
• ENCRYPTED: specifies whether the password is stored in an encrypted format
• VALID UNTIL: specifies when the user's account will expire
• IN ROLE: assigns the new user to a specific role
• IN GROUP: assigns the new user to a specific group
• CREATEDB: allows the user to create new databases
• CREATEROLE: allows the user to create new roles
• CREATEUSER: allows the user to create new users

For example, to create a new user named 'johndoe' with the password 'password' and assign it to the 'developers' role, you would use the following command:

CREATE USER johndoe PASSWORD 'password' IN ROLE developers;

Modifying Users in PostgreSQL
To modify an existing user in PostgreSQL, you can use the ALTER USER SQL command. The basic syntax for modifying a user is as follows:

ALTER USER <username> [OPTIONS];

The options available for the ALTER USER command include:

• PASSWORD: changes the password for the user
• RENAME TO: renames the user
• IN ROLE: assigns the user to a specific role
• IN GROUP: assigns the user to a specific group
• CREATEDB: allows the user to create new databases
• CREATEROLE: allows the user to create new roles
• CREATEUSER: allows the user to create new users

For example, to change the password of the user 'johndoe' to 'newpassword', you would use the following command:

ALTER USER johndoe PASSWORD 'newpassword';

Deleting Users in PostgreSQL
To delete an existing user in PostgreSQL, you can use the DROP USER SQL command. The basic syntax for deleting a user is as follows:

DROP USER <username>;

For example, to delete the user 'johndoe', you would use the following command:

DROP USER johndoe;

Creating Roles in PostgreSQL
To create a new role in PostgreSQL, you can use the CREATE ROLE SQL command. The basic syntax for creating a new role is as follows:

CREATE ROLE <rolename> [OPTIONS];

The options available for the CREATE ROLE command include:

• PASSWORD: sets the password for the new role
• ENCRYPTED: specifies whether the password is stored in an encrypted format
• LOGIN: allows the role to be used as a user to log in to the system
• SUPERUSER: grants the role superuser privileges
• CREATEDB: allows the role to create new databases
• CREATEROLE: allows the role to create new roles
• CREATEUSER: allows the role to create new users

For example, to create a new role named 'developers' with the password 'password' and allow it to login and create new databases, you would use the

Popular questions

1. How do you list all users in a PostgreSQL database?
   Answer: To list all the users in a PostgreSQL database, you can use the following SQL query: SELECT usename FROM pg_user;

2. How do you list all roles in a PostgreSQL database?
   Answer: To list all the roles in a PostgreSQL database, you can use the following SQL query: SELECT rolname FROM pg_roles;

3. How do you list both users and roles in a PostgreSQL database?
   Answer: To list both users and roles in a PostgreSQL database, you can use the following SQL query:

SELECT usename as name, 'user' as type FROM pg_user
UNION
SELECT rolname as name, 'role' as type FROM pg_roles;

4. How do you list the roles assigned to a specific user?
   Answer: To list all roles of a specific user, you can use the following SQL query:

SELECT rolname FROM pg_roles
WHERE oid IN (
  SELECT roleid FROM pg_auth_members
  WHERE member = (SELECT usesysid FROM pg_user WHERE usename='<username>')
);

Replace with the name of the user you want to query.

5. How do you list the users assigned to a specific role?
   Answer: To list all users in a specific role, you can use the following SQL query:

SELECT usename FROM pg_user
WHERE usesysid IN (
  SELECT member FROM pg_auth_members
  WHERE roleid = (SELECT oid FROM pg_roles WHERE rolname='<rolename>')
);

Replace with the name of the role you want to query.

Tag

PostgreSQL