NATURAL JOIN
intermediatejoins
2 min read
What is a NATURAL JOIN?
A NATURAL JOIN automatically matches columns that have the same name in both tables. You do not specify an ON or USING clause — PostgreSQL infers the join condition.
Syntax
SELECT * FROM table1
NATURAL JOIN table2;When to Use
- Quick exploration when tables share obvious key column names
- Simple queries in controlled environments
- Prototyping (but switch to explicit joins for production)
Key Points
- Auto-Matching — PostgreSQL joins on all columns with matching names in both tables.
- No Duplicate Columns — Matching columns appear only once in the result.
- Fragile — Adding a column with a matching name silently changes the join condition.
- Not Recommended for Production — Explicit JOIN ON is safer and clearer.
- Variants — NATURAL LEFT JOIN, NATURAL RIGHT JOIN, and NATURAL FULL JOIN also exist.
Guided Practice
Solve the challenge below. Use hints when stuck and check your answer for instant feedback.
Practice challengeGuided learning mode
NATURAL JOIN Challenge
Write a query that solve this task: join on automatically matched column names.
Expected result
Joined on columns with the same name (e.g., id or student_id depending on schema). Matching columns appear once.
Hidden checks
- Returned rows and values
- Output columns and result shape
- Final database state after the query runs
Lesson guidance
What is a NATURAL JOIN?
Initializing database...Each run starts from fresh sample data.
More Examples
Natural left join
Keep all students even without enrollments.
Initializing database...Each run starts from fresh sample data.
Frequently Asked Questions
Why is NATURAL JOIN considered risky?
It silently joins on all same-named columns. Adding a new column with a common name (like 'name' or 'id') can break queries without any visible change in the SQL.
Is NATURAL JOIN the same as INNER JOIN?
NATURAL JOIN performs an inner join by default, but the join condition is inferred from matching column names rather than specified explicitly.