A NATURAL JOIN automatically matches columns with the same names between two tables. The database determines the matching columns without an explicit ON condition.
NATURAL JOIN can create unexpected results when tables contain columns with the same name that are not intended to define a relationship.
Two tables containing CustomerID with the same name may be automatically matched by a NATURAL JOIN.
SELECT
CustomerName,
OrderID
FROM Customers
NATURAL JOIN Orders;The concept is useful for understanding SQL JOIN behavior, although explicit JOIN conditions are generally easier to control and maintain.
- NATURAL JOIN uses same-named columns automatically.
- It does not require an explicit ON condition.
- Unexpected same-named columns can affect results.
- Explicit JOIN conditions provide better control.
- Database support can vary.
What is NATURAL JOIN?
NATURAL JOIN automatically joins tables using columns that have matching names.
Why can NATURAL JOIN be risky?
A newly added same-named column can unintentionally change the JOIN behavior.