ORDER BY clause with Alias I am trying to get the sum of the market values for each given CPTY. Each CPTY can have several market values. In my output list, i want to see the top 5 CPTYs, ordered by the sum of their market values. 

Works:

SELECT TOP 5 CPTY, SUM( MKT_VAL ) AS MarketVal
FROM Eod
GROUP BY CPTY
ORDER BY SUM( MKT_VAL ) DESC;


Fails:

SELECT TOP 5 CPTY, SUM( MKT_VAL ) AS MarketVal
FROM Eod
GROUP BY CPTY
ORDER BY MarketVal DESC;


It appears when I try to ORDER BY the Alias (MarketVal), Access asks for MarketVal parameter value. However, when I ORDER BY SUM( MKT_VAL ), the code executes fine. I can't understand why this is, can anyone tell me why?
There is no issue in both the query they will run properly.

you must inspect any expressions Or find the identifier that is causing this.