PostgreSQL is one of the most widely used databases in the world & is also very easy to administer. In this tutorial, we will learn some important postgresql commands that every beginner should know.
In our previous tutorials, we have learned to install postgresql on CentOS/RHEL, on Ubuntu & also learned to install Postgresql from source. So if you need to install postgresql first, please refer to those tutorials.
Recommended Read: Scheduling CRON Jobs with Crontab for Beginners
Also Read: Beginner’s guide to Backup Postgres Database
PostgreSQL commands
1- Connect to the database
Connection from localhost,
# su – postgres
Now to connect to the database, we will run the command ‘psql’,
$ psql
Once into the database, we can use ‘\q’ to exit the database,
postgres=# \q
Connecting from Remote server,
# psql -h host_ip -U user_name -p port_number -d database_name
2- Create role/user
To create a role, first connect to database & then we will use command ‘createuser’,
postgres=# CREATE USER test;
Or we can also use the following,
postgres=# CREATE ROLE test;
To create a user with password,
$ CREATE USER test PASSWORD ‘enter password here’
3- Delete a role/user
To delete a role, we will use the DROP command,
postgres=# DROP ROLE test;
4- Show list of users (List of roles)
postgres=# \du
5- Create a new Database
To create a new database, use the following,
postgres=# CREATE DATABASE thelinuxgurus;
6- Delete a database
To delete a created database, use
postgres=# DROP DATABSE thelinuxgurus;
7- Show list of databases
postgres=# \l
8- Change DB when you are connected to other DB
postgres=# \c thelinuxgurus;
Or we can also user the following command,
postgres-# \connect new_database
9- Create a table
To create a table, connect to the desired database & create a table with the following command,
thelinuxgurus=> CREATE TABLE USERS (Serial_No int, First_Name varchar, Last_Name varchar);
Now insert some records into it,
thelinuxgurus=> INSERT INTO USERS VALUES (1, ‘Dan’, ‘Prince’);
10- Delete a table
To delete a table from the database, we will use,
thelinuxgurus=> DROP TABLE USERS;
11- List tables
postgres=# \dt
12- Describe a table to show its structure
postgres=# \d table_name
13- Adding a column to a table
Once a table has been created, it can be altered to add new columns to it using the following command,
thelinuxgurus=> ALTER TABLE USERS ADD date_of_birth date;
14- Updating a Row
We can not only alter the columns of a table but can also update the records that are entered in rows,
thelinuxgurus=> UPDATE USERS SET date_of_birth = ‘03-04-1990’ WHERE Seriel_No = ‘1’;
thelinuxgurus=> SELECT * FROM USERS;
The last command was to verify the changes that were made.
15- Remove a Column
To remove a column from a table, run
thelinuxgurus=> ALTER TABLE USERS DROP date_of_birth;
16- Remove a Row
To delete a row, use the following example,,
thelinuxgurus=> DELETE FROM USERS WHERE Seriel_No = ‘1’;
17- List of all functions
To check all the functions on the database, use
postgres=# \df
18- To edit function
To edit a function, use the following command,
postgres=# \ef function_name
19- List of all schema in DB
To see all the schemas on the database, use
postgres=# \dn
20- To check the current Installed version
postgres=# select version();
21- To display the command history
postgres=# \s
22- Execute psql commands using a file
So if we have a file (like a .sql file) & we need to execute the file into our database, then use the following command
postgres=# \i /path/file_name
23- To turn on query execution time
postgres=# \timing
24) To list database views
postgres=# \dv
25) Check current date
postgres=# select now();
These were some of the important PostgreSQL commands that everyone should know about to maintain & administer the PostgreSQL database. Please feel free to send in any question or queries using the comment box below.
