Question

I can’t figure out what I am doing wrong with my query here.

SELECT ORDER#, SUM(PAIDEACH * QUANTITY) AS TOTAL 
    FROM ORDERITEMS 
    WHERE TOTAL > 39.9 
    GROUP BY ORDER# 
    ORDER BY TOTAL DESC; 

This is the error I keep getting:

"TOTAL": invalid identifier

Answer 1

Since you want to have a predicate on your aggregate function, you can use a HAVING clause

SELECT ORDER#, SUM(PAIDEACH * QUANTITY) AS TOTAL 
  FROM ORDERITEMS 
 GROUP BY ORDER# 
HAVING SUM(PAIDEACH * QUANTITY) > 39.9
 ORDER BY TOTAL DESC;