How to assign a sum of values within fields to a variable?

Question

I have an SQL statement which selects various data from a table in my database and I have declared variables within my code like:

DECLARE @TotalAge int;

Let's say one of the fields in the table is Age, how would I sum the collected values from the query and assign them to the variable as a total?

Answer 1

First set @TotalAge:

set @TotalAge=(select sum(Age) from TableName)

then select @TotalAge where you want:

select @TotalAge