My SQL Tutorials - Sum
Computing a Column Total (SUM):
The SUM() column function computes the sum of a column of data values. The data in the column must have a numeric type. This result must have the same basic data type as the data in the column, however the result may have a higher precision. Here is an example of the SUM() column function...
Select Sum(Internet_Length)
From Internet_Use_Table
Where User equals "Steve";