Natural join

A natural join is a join statement that compares the common columns of both tables with each other. One should check whether common columns exist in both tables before doing a natural join.

Natural joins may cause problems if columns are added or renamed.

Examples

This is the same as an equi join on (emp.deptno = dept.deptno):

SELECT dname, ename FROM dept NATURAL JOIN emp

Same query on the HR sample schema:

SELECT department_name, first_name||' '||last_name
  FROM departments NATURAL JOIN employees;

Also see

• Cartesian join
• Equi join
• Inner join
• Nonequi join
• Outer join
• Self join

Glossary of Terms
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