If I understand correctly, you need something like this.

SELECT SUM( CASE WHEN age BETWEEN 18 AND 25 THEN MyValue END) AS [18-25],

SUM( CASE WHEN age BETWEEN 26 AND 35 THEN MyValue END) AS [26-35],

SUM( CASE WHEN age BETWEEN 36 AND 45 THEN MyValue END) AS [36-45],

SUM( CASE WHEN age > 45 THEN MyValue END) AS [18-25]

FROM myTable

Otherwise, you should post more details. Please read the article linked on my signature to find out how to get better help. 😉