How can I create a row for values that don't exist and fill the count with 0 values?

Question

In SQL Server, I\'m running a query on users age groups on data where, for some years, there are zero users per age group. For example there were users in 2013 in the \"18-21\"

Answer 1

I assume you have another table that contain all rows Age Group.

TABLE NAME: AGEGROUPS

AGE_GROUP
18-21
22-25
25-28

Try this:

SELECT '2014' AS YEAR, AG.AGE_GROUP, COALESCE(TB.usercount, 0) AS usercount
FROM (
    SELECT YEAR, AGE_GROUP, SUM(USERS) as usercount,
    FROM USERS
    WHERE YEAR = '2014'
    AND PRIMARY_GROUP = 'NT'
    GROUP BY YEAR, AGE_GROUP
) AS TB
RIGHT JOIN AGEGROUPS AG ON TB.AGE_GROUP=AG.AGE_GROUP