query of queries question

HI All -

I have a query which returns the result set like below. The column names are like 1990, 1991, 1992 and there are certain amount for each year

1990 1991 1992
1000 5000 6000
2000 2000 3000

I have a query of query which finds the sum of the amounts for year 1990, and I use the query like Select SUM(1990), it returns the sum of 1990+1990. How to make sure that 1990 is recognized as a column instead as a number.

Thanks