PostgreSQL Create, Alter, Add, Drop USER

Step 8) In the command line you can see the owner is “myguru”

PostgreSQL Create a User SQLShell (Command Line)

You can create a user by using the command-line command

CREATE USER

In PostgreSQL, this method is more convenient for programmers and administrators as they have access to the console of PostgreSQL server. Moreover, they need to execute with a single command in place of logging in and using the interface of the PostgreSQL client.

Syntax:
CREATE USER name WITH option

where the option can be:

|SUPERUSER | NOSUPERUSER 
| CREATEROLE | NOCREATEROLE 
| CREATEDB | NOCREATEDB 

| INHERIT | NOINHERIT 

| LOGIN | NOLOGIN 

| REPLICATION | NOREPLICATION 

| BYPASSRLS  | NOBYPASSRLS 

| CONNECTION LIMIT 

| ( ENCRYPTED ] PASSWORD 'password.' 

| VALID UNTIL 'timestamp1 

| IN ROLE role_name [, ...J 

| IN GROUP role_name [, ...]

| ROLE role_name [, ...]

| ADMIN role_name [, ...)

| USER role_name [, ...]

| SYSID uid

Example:

CREATE USER tom;

will create a user tom

CREATE USER tom WITH SUPERUSER;

Will create a user tome with superuser privileges. Let’s see the following example.

Step 1) We are creating a superuser valid till 3^rd Apri 2025 11:50:38 IST. Enter the following command

CREATE USER mytest WITH
	LOGIN
	SUPERUSER
	CREATEDB
	CREATEROLE
	INHERIT
	NOREPLICATION
	CONNECTION LIMIT -1
	VALID UNTIL '2025-04-03T11:50:38+05:30' 
	PASSWORD '123456';

Step 2) Enter command \du into the checklist of users

NOTE: CREATE USER is same as CREATE ROLE command. The difference between the two commands is when the CREATE USER command is written it is by default in the LOGIN state whereas NOLOGIN is assumed when the CRETE ROLE option is used.

Add an existing user to a Database

You can grant a user privileges to access a database.

Example, we grant user “mytest” all privileges on user guru99

GRANT ALL PRIVILEGES ON DATABASE guru99 TO mytest;

After execution of this command user will able to access the database with the given permissions.

The command GRANT is very powerful. You can give granular privileges like Select, Insert, Update to a user.

PostgreSQL Updating USER

Altering Existing User Permissions

Now that our new user “mytest” exists you can use ALTER USER to change the permissions granted to the librarian.

The format of ALTER USER includes the name of the user followed by some options to tell PostgreSQL which permissive alterations to make:

ALTER USER role_specification WITH OPTION1 OPTION2 OPTION3;

Revoking Permissions

You need to use this command when you make a mistake and wrongly assign permission which you may want to revoke. You can use ALTER USER command with no prefix before the permissive options.

For example, we can remove the SUPERUSER status from mytest like:

ALTER USER mytest WITH NOSUPERUSER;

Using \du, you will observe that the Superuser privilege is removed.

Assigning Permission

You can use user SUPERUSER permission back “mytest” using the following command

ALTER USER mytest WITH SUPERUSER;

Using \du, you will observe that the Superuser privilege is added.

PostgreSQL Deleting User

You can use delete any user if you are sure that the specific user is no longer for your database. Note that deleting the users will never affect the actual database.

Syntax: DROP USER [user]

To delete any user, you have to make certain that the user is an owner of the database. Otherwise, you may receive an error message.