Joining Tables and Identifying Columns

ON Clause

You use the ON clause to specify the join condition when joining two tables or joining a table to itself. This enables you to separate the join condition from any search or filter conditions in the WHERE clause. The column names need not match between the tables; however, the data types must match.

Syntax

SELECT [DISTINCT] * | column [alias], ...
FROM table1 JOIN table2
ON col_name_1 = col_name_2

For example, Shelia might need to evaluate the hire dates and start dates of all employees. She can find the hire dates in the EMPLOYEES table and the start dates in the JOB_HISTORY table. These two columns are named differently. The ON clause is as follows:

FROM employees JOIN job_history
ON employees.hire_date = job_history.start_date