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

Answer 2

You do this by joining with a "fake" list of age group+years:

SELECT AGE_GROUPS.YEAR, AGE_GROUPS.AGE_GROUP, COALESCE(SUM(USERS), 0) as usercount
FROM (
    SELECT YEAR, AGE_GROUP
    FROM (
        SELECT '18-21' AS AGE_GROUP
        UNION SELECT '22-25'
        UNION SELECT '25-28'
    ) AGE_GROUPS, (SELECT DISTINCT YEAR FROM USERS) YEARS
) AGE_GROUPS
LEFT JOIN USERS ON (USERS.AGE_GROUP = AGE_GROUPS.AGE_GROUP AND USERS.YEAR = AGE_GROUPS.YEAR)
WHERE AGE_GROUPS.YEAR = '2014'
GROUP BY AGE_GROUPS.YEAR, AGE_GROUPS.AGE_GROUP

You can also simplify this, assuming that your USERS table has all possible age groups ignoring a specific year:

SELECT AGE_GROUPS.YEAR, AGE_GROUPS.AGE_GROUP, COALESCE(SUM(USERS), 0) as usercount
FROM (
    SELECT YEAR, AGE_GROUP
    FROM (SELECT DISTINCT AGE_GROUP FROM USERS) AGE_GROUPS, (SELECT DISTINCT YEAR FROM USERS) YEARS
) AGE_GROUPS
LEFT JOIN USERS ON (USERS.AGE_GROUP = AGE_GROUPS.AGE_GROUP AND USERS.YEAR = AGE_GROUPS.YEAR)
WHERE AGE_GROUPS.YEAR = '2014'
GROUP BY AGE_GROUPS.YEAR, AGE_GROUPS.AGE_GROUP

Answer 3

Try This...

SELECT YEAR, AGE_GROUP, isnull(Sum(USERS),0) as usercount,
FROM USERS
 WHERE YEAR = '2013'
AND PRIMARY_GROUP = 'NT'
GROUP BY YEAR, AGE_GROUP

Answer 4

Assuming that all the years and age groups are in the table (some row for the table), then you can do this just with this table. The idea is to generate all the rows using a cross join and then use a left join to bring in the values you want:

select y.year, ag.age_group, count(u.year) as usercount
from (select 2013 as year) y cross join
     (select distinct age_group from users) ag left join
     users u
     on u.year = y.year and u.age_group = ag.age_group and
        u.primary_group = 'NT'
group by y.year, ag.age_group;

I don't know what sum(users) is supposed to be. If you do indeed have a column users.users, then use it with sum(). It looks like you really want count().