Postgres and Open Source Experts

To install PostgreSQL on your Ubuntu operating system, run the “sudo apt install postgresql postgresql -contrib” command.

psycopg is a Postgres Python connector that allows Python programs to access Postgres databases. It is used to perform various operations on Postgres database via python.

In PostgreSQL, the “ILIKE” operator is used to fetch/query the data based on pattern matching. The ILIKE operator queries the data case-insensitively.

In Postgres, the DROP USER statement is used to drop a single user or multiple users simultaneously. Use IF EXISTS option to check the existence of a user.

Use the ALTER USER or ALTER ROLE statement to change/modify the password of a Postgres user. You can use the VALID UNTIL clause to specify the password’s expiry date and time.

Use the ADD CONSTRAINT or DROP CONSTRAINT clause with the ALTER TABLE command to add or drop a primary key constraint from a Postgres table.

Postgres offers a couple of standard tools/utilities, such as pg_dump and pg_dumpall, to back up a single or all databases.

Install “psycopg2” module, import it into your python program, and use the connect() function of “psycopg2” module to connect to the Postgres database server via python.

Postgres provides an ARRAY_APPEND() function that is used to append/add elements at the end of the array. It accepts two parameters: an array and an element to be appended.

To get the first non-null value in Postgres, an inbuilt function named COALESCE() is used. It accepts the “n” number of arguments and retrieves the first non-null value.