Create column-reference for PostgreSQL.

[ogumbaiyke]

Description

I made a summary of column reference and how to use it to get information from databases. Motivation includes just learning and growing in tech.

Issue Solved

Fixes #4536

Issues solved includes understanding of column reference in simple terms, clear syntax lines of code with good comments that can aid better understanding of topic and usage of syntax and applying column reference.

Type of Change

• Adding a new entry

Checklist

• All writings are my own.
• My entry follows the Codecademy Docs style guide.
• My changes generate no new warnings.
• I have performed a self-review of my own writing and code.
• I have checked my entry and corrected any misspellings.
• I have made corresponding changes to the documentation if needed.
• I have confirmed my changes are not being pushed from my forked main branch.
• I have confirmed that I'm pushing from a new branch named after the changes I'm making.
• I have linked any issues that are relevant to this PR in the Issues Solved section.

[CLAassistant]

All committers have signed the CLA.

[Sriparno08]

Hey @ogumbaiyke, thanks for contributing to Codecademy!

I've listed all the modifications that you need to make in your entry below:

[ogumbaiyke]

Thanks. I have made the required changes.