Understanding Natural Join in SQL

Estimated study time: 8 minutes. A join that matches columns automatically by name.

A NATURAL JOIN automatically joins two tables based on all columns that share the same name and compatible data type — no ON clause required.

Basic Syntax

SELECT *
FROM TableA
NATURAL JOIN TableB;

A Practical Example

If both Employees and Departments have a column named DeptID, a natural join uses it automatically:

SELECT *
FROM Employees
NATURAL JOIN Departments;

This behaves like an INNER JOIN ON Employees.DeptID = Departments.DeptID, but without writing the condition explicitly.

Why It's Risky

Natural joins match on every identically named column, whether you intended that or not. If both tables happen to also share a column like CreatedDate, it silently becomes part of the join condition too — often producing far fewer rows than expected.

SQL Server Note

SQL Server does not implement the NATURAL JOIN keyword directly (unlike MySQL or Oracle). The same result is achieved with a regular INNER JOIN and an explicit ON clause naming the shared columns.