Beginner

642. NATURAL LEFT JOIN

Learn how NATURAL LEFT JOIN preserves all rows from the left table while automatically matching common columns.

📘 Lesson 642 of 728 ⏱ 13 min 🎯 Intermediate

NATURAL LEFT JOIN combines tables using automatically detected common columns while retaining all rows from the left table.

It demonstrates how automatic matching can be combined with outer-join behavior, although explicit JOIN conditions are generally safer.

Return all employees and their department information where matching columns exist.

SQL 
SELECT
    EmployeeName,
    DepartmentName
FROM Employees
NATURAL LEFT JOIN Departments;

Primarily useful for understanding SQL behavior and controlled schemas.

  • All left-table rows are preserved.
  • Common columns are used automatically.
  • Unmatched right-side values become NULL.
  • Unexpected common columns can affect results.
  • Explicit LEFT JOIN is generally more predictable.
What does NATURAL LEFT JOIN preserve?

It preserves every row from the left table, including rows without a matching row on the right.

What happens when no matching right row exists?

Columns from the right table are returned as NULL.

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