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Articles & Tutorials

Additional educational materials on SQL, not included in the main course

SELECT *
Fundamentals
7 min read

SQL from Scratch: A Step-by-Step Learning Plan for Beginners in 2026

A 6-week roadmap — from your first SELECT to the interview

3NF
Fundamentals
6 min read

Database Normalization: Normal Forms Explained Simply

1NF, 2NF and 3NF on a single running example

RANK()
SQL in practice
3 min read

ROW_NUMBER vs RANK vs DENSE_RANK in SQL: The Difference in One Example

Three ranking functions, one query — and the difference is visible

ACID
Fundamentals
7 min read

ACID: The 4 Properties of Database Transactions Explained Simply

Atomicity, consistency, isolation, durability — through a money transfer example

COALESCE()
SQL in practice
6 min read

SQL COALESCE: What It Is and How It Works — Examples | SQL Academy

The first non-NULL argument, and why NULLIF belongs nearby

WITH … AS
SQL in practice
4 min read

CTE in SQL: What a Common Table Expression (WITH) Is — Examples

Subqueries with names, chains of steps, and recursion

DATEDIFF()
SQL in practice
4 min read

DATEDIFF in SQL: How to Calculate the Difference Between Dates (MySQL, PostgreSQL)

Days, hours, months and age — each DBMS does it differently

EXPLAIN
Performance
7 min read

SQL Query Optimization: 10 Ways to Speed Up a Slow Query

From EXPLAIN to proper pagination — a practical checklist

CONCAT()
SQL in practice
5 min read

SQL String Functions: CONCAT, SUBSTRING, TRIM, REPLACE — Cheat Sheet

Join, cut, clean and search — with live examples

TRUNCATE
SQL in practice
5 min read

TRUNCATE vs DELETE vs DROP in SQL: The Difference and What to Choose

The three deletion commands people confuse most often

PIVOT
SQL in practice
6 min read

PIVOT in SQL: How to Turn Rows into Columns

Building pivot tables with pure SQL

SEQUENCE
SQL in practice
6 min read

SQL SEQUENCE in PostgreSQL: one ID generator for multiple tables

Solving the shared document numbering problem