Joining Three Tables

How to Join Three Tables

To combine data from three tables, chain multiple JOIN clauses. Each JOIN connects two tables via a shared key. This is common with bridge/junction tables.

Syntax

SELECT columns
FROM table1
JOIN table2 ON table1.key = table2.fk
JOIN table3 ON table2.key2 = table3.fk;

When to Use

• Connecting entities through a junction table (students → enrollments → courses)
• Building reports that span multiple related tables
• Any time you need data from three or more tables in one query

Key Points

1. Chain JOINs — Each JOIN clause adds one more table to the query.
2. Junction Tables — Many-to-many relationships require a bridge table in the middle.
3. Aliases — Use short aliases (s, e, c) to keep the query readable.
4. Mix Types — You can mix INNER JOIN, LEFT JOIN, etc. in the same query.
5. Order — Start with the table that makes the most logical sense, then join related tables.