How To Write a Query with an Inner Join? - Oracle DBA FAQ - Understanding SQL SELECT Query Statements

If you want to query from two tables with an inner join, you can use the INNER JOIN ... ON clause in the FROM clause. The following query returns output with an inner join from two tables: employees and departments. The join condition is that the department ID in the employees table equals to the department ID in the departments table:

SQL> SELECT employees.first_name, employees.last_name, 
  2  departments.department_name 
  3  FROM employees INNER JOIN departments 
  4  ON employees.department_id=departments.department_id;
FIRST_NAME           LAST_NAME            DEPARTMENT_NAME
-------------------- -------------------- ---------------
Steven               King                 Executive
Neena                Kochhar              Executive
Lex                  De Haan              Executive
Alexander            Hunold               IT
Bruce                Ernst                IT
David                Austin               IT
Valli                Pataballa            IT
......

Note that when multiple tables are used in a query, column names need to be prefixed with table names in case the same column name is used in both tables.