Sams Teach Yourself SQL in 24 Hours, Second Edition

Using an ORDER BY with a Compound Query

The ORDER BY clause can be used with a compound query. However, the ORDER BY can only be used to order the results of both queries. Therefore, there can be only one ORDER BY clause in a compound query, even though the compound query may consist of multiple individual queries or SELECT statements. The ORDER BY must reference the columns being ordered by an alias or by the number of column order.

The syntax is as follows:

SELECT COLUMN1 [, COLUMN2 ]
FROM TABLE1 [, TABLE2 ]
[ WHERE ]
OPERATOR{UNION | EXCEPT | INTERSECT | UNION ALL}
SELECT COLUMN1 [, COLUMN2 ]
FROM TABLE1 [, TABLE2 ]
[ WHERE ]
[ ORDER BY ]

Examine the following example:

 SELECT EMP_ID FROM EMPLOYEE_TBL UNION SELECT EMP_ID FROM EMPLOYEE_PAY_TBL ...