ORDER BY clause with UNION

As the following query shows, when you include an ORDER BY clause, it must follow the final SELECT statement and use an integer, not an identifier, to refer to the ordering column. Ordering takes place after the set operation is complete.

SELECT DISTINCT stock_num, manu_code FROM stock
   WHERE unit_price < 25.00
UNION
SELECT stock_num, manu_code FROM items
   WHERE quantity > 3 
   ORDER BY 2;

The compound query above selects the same rows as Query but displays them in order of the manufacturer code, as the result shows.

stock_num manu_code

        5 ANZ
        9 ANZ
      302 HRO
      301 KAR
      302 KAR
      201 NKL
        5 NRG
      103 PRC
      106 PRC
        5 SMT