Joins

Real data lives across multiple tables. Joins are how you bring it together. This course covers every join type so you always know exactly which rows will appear in your result — and which ones won't.

What you'll learn

• INNER JOIN — only rows with a match in both tables
• LEFT JOIN — all left-side rows; NULLs where there is no match on the right
• RIGHT JOIN — the mirror of LEFT JOIN
• FULL OUTER JOIN — everything from both sides, NULLs to fill gaps
• Self-joins — joining a table to itself (classic use: employees and their managers)
• Multi-table joins — chaining three or more tables in one query
• ON vs USING — when to use each

What you'll practice on

The HR database (employees ↔ departments ↔ jobs) and the Store database (orders ↔ customers ↔ products). You'll answer questions that are simply impossible with a single table.

Prerequisites

SQL Fundamentals + Filtering & Logic. Aggregations & Grouping is helpful but not required.