Oracle Database Administration: The Essential Refe

Joins

A join is the relational operator that combines information from two or more tables. The WHERE clause specifies how the tables are to be combined. In a database with referential constraints enabled, this is usually accomplished by matching foreign keys to primary keys. An example of a join is:

SELECT emp.ename, emp.empno, emp.job, dept.dname 
FROM emp, dept
WHERE emp.deptno = dept.deptno;