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SQL & Databases

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SQL Fundamentals5

Joins & Aggregation5

Joins: the set theory behind combining tables
Aggregate functions and GROUP BY
Subqueries and CTEs - thinking in multiple steps
Window functions - per-row analytics without collapsing rows
Self-joins, EXISTS, and conditional aggregation

Design & Normalization4

Transactions & Performance4

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SQL & Databases

Database Foundations4

SQL Fundamentals5

Joins & Aggregation5

Joins: the set theory behind combining tables
Aggregate functions and GROUP BY
Subqueries and CTEs - thinking in multiple steps
Window functions - per-row analytics without collapsing rows
Self-joins, EXISTS, and conditional aggregation

Design & Normalization4

Transactions & Performance4

PostgreSQL Deep Dive4

MySQL & MariaDB4

NoSQL & Choosing the Right Database5

Advanced SQL Toolkit5

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Joins: the set theory behind combining tables

INNER, LEFT, RIGHT and FULL joins explained with Venn diagrams, foreign keys, and the Cartesian product they're all built from.

13 min readUpdated 2026-09-04sqljoinsrelational-algebra