Databases & SQL
intermediateTopic 6 of 12 in Backend Development
What it is
A database stores your application's data in an organised way. SQL (Structured Query Language) is the standard language for interacting with relational databases like PostgreSQL, MySQL, and SQLite.
Why backend developers need it
Every real application needs to store data — users, orders, posts, messages. Understanding databases lets you design efficient data models and write queries that perform well at scale.
What to learn
Relational vs. non-relational databases
Tables, rows, columns, and primary keys
SQL: SELECT, INSERT, UPDATE, DELETE
JOINs: combining data from multiple tables
Indexes and query performance
Database design: normalisation, relationships, foreign keys
Migrations: managing schema changes over time
Introduction to PostgreSQL
Practice project
Student Database
Design and build a PostgreSQL database for a school: students, courses, enrolments, and grades. Write queries to find top students, course enrolment counts, and average grades per course.