DEV Community

Cover image for SQL Fundamentals: What is SQL and How Databases Work
QAPulse by SK
QAPulse by SK

Posted on Originally published at skakarh.com

SQL Fundamentals: What is SQL and How Databases Work

#databasetesting #database #mysql #postgres

Why SQL Fundamentals Matter Before Learning SQL Syntax

SQL is often introduced as a list of commands:

SELECT
INSERT
UPDATE
DELETE
CREATE
ALTER
DROP
Enter fullscreen mode Exit fullscreen mode

That approach teaches syntax, but it does not necessarily teach understanding.

A stronger learning path begins with a more fundamental question:

What problem is SQL solving?

Modern applications constantly create, retrieve, modify, and delete information.

A banking application needs customer and transaction data.

An e-commerce application needs products, customers, orders, payments, and inventory.

A testing system needs test cases, executions, defects, environments, and results.

The application needs a reliable place to store that information and a structured way to communicate with it.

That is where databases and SQL enter the picture.

Understanding SQL fundamentals therefore means understanding the complete relationship between:

Application → Database → DBMS → SQL → Query → Result

Once that mental model is clear, SQL commands become much easier to learn.

What is SQL?

SQL stands for Structured Query Language.

It is a standardized language used to interact with relational databases.

SQL allows applications and engineers to perform operations such as:

  • Retrieving data
  • Inserting data
  • Updating existing data
  • Deleting data
  • Creating database structures
  • Modifying database structures
  • Controlling access
  • Managing transactions

A simple query looks like this:

SELECT name, email
FROM customers
WHERE country = 'Pakistan';
Enter fullscreen mode Exit fullscreen mode

Conceptually, the query says:

Find the name and email values from customers whose country is Pakistan.

Find the name and email values from customers whose country is Pakistan.

SQL is therefore not the database itself.

This distinction is critical.

SQL is the language.

The database stores the data.

The DBMS manages the database.

For example, PostgreSQL, MySQL, Microsoft SQL Server, and Oracle Database are database management systems that support SQL.

SQL is Declarative

One of the most important concepts in SQL fundamentals is that SQL is primarily declarative.

You describe what data you want, rather than manually specifying every step the database must execute.

For example:

SELECT *
FROM orders
WHERE status = 'PAID';
Enter fullscreen mode Exit fullscreen mode

The engineer specifies the desired result.

The database engine decides how to retrieve it efficiently.

This is different from writing an algorithm that manually loops through every record and checks its status.

What is a Database?

A database is an organized collection of data designed to allow information to be stored, managed, retrieved, and modified efficiently.

Consider an online shopping system.

It might contain:

Instead of putting everything into one enormous file, a relational database organizes information into structured tables.

A simplified database might look like:

E-Commerce Database
│
├── customers
├── products
├── orders
├── order_items
├── payments
└── reviews
Enter fullscreen mode Exit fullscreen mode

Each table represents a particular type of entity or relationship.

Database vs DBMS vs RDBMS

These terms are frequently confused.

Database

The database contains the information.

DBMS

The Database Management System provides the software infrastructure for storing and manipulating that information.

RDBMS

A Relational Database Management System organizes data using relational concepts such as tables, keys, and relationships.

Common relational database systems include:

  • PostgreSQL
  • MySQL
  • Microsoft SQL Server
  • Oracle Database
  • SQLite

The exact implementation differs between systems, but the fundamental relational concepts remain highly transferable.

How Relational Databases Organize Data

A relational database represents information through tables.

Consider a customers table:

The table consists of:

  • Columns — describe attributes
  • Rows — represent individual records
  • Values — actual pieces of stored data

Columns

A column represents one attribute.

Examples:

customer_id
name
email
country
Enter fullscreen mode Exit fullscreen mode

Rows

A row represents one record.

For example:

101 | Ali Khan | ali@example.com | Pakistan
Enter fullscreen mode Exit fullscreen mode

Values

Individual values occupy the cells.

👉 Continue reading the full article on skakarh.com →

Originally published at skakarh.com/sql-fundamentals.
Subscribe to QA Pulse by SK —
weekly signal for QA, Test Automation and AI in Software Engineering.

Top comments (0)