Count, Having and Case statement - sql

Question

I'm looking to produce a count of projects based on 3 different conditions (DB2 database). I need to count all projects <= .10, >= .5, and >= 1.00 (percentage_used) but can only group by dim_building_id and building_name. Of course this query will not run because it requires percentage_used to be added to the group by. How do I handle those 3 conditions with percentage_used?
SELECT
SUM(CAST(FTS.GROUP_A AS BIGINT)) AS GROUP_A,
SUM(CAST(FTS.GROUP_B AS BIGINT)) AS GROUP_B,
SUM(CAST(FTS.GROUP_C AS BIGINT)) AS GROUP_C,
CASE WHEN FAT.PERCENTAGE_USED <= '0.10'
THEN COUNT(*)
END AS PROJECTS_L10,
CASE WHEN FAT.PERCENTAGE_USED >= '0.50'
THEN COUNT(*)
END AS PROJECTS_G50,
CASE WHEN FAT.PERCENTAGE_USED >= '1.00'
THEN COUNT(*)
END AS PROJECTS_G100,
DAYS(DATE('2014-07-01')) - DAYS(CURRENT DATE) AS DAYS_LEFT,
(DAYS(DATE('2014-07-01')) - DAYS(CURRENT DATE))/7 AS WEEKS_LEFT,
DAYS(DATE('2013-12-31')) - DAYS(CURRENT DATE) AS DAYS_LEFT_YEAR
FROM FACT_TABLE AS FAT
INNER JOIN GROUPS AS FTS ON FAT.DIM_PROJECT_ID = FTS.DIM_PROJECT_ID
GROUP BY FAT.DIM_BUILDING_ID, FAT.BUILDING_NAME;

Answer 1

I'd do something like this:
select bn.building_name ,
t.*
from ( select fat.building_id ,
sum( case when fat.percentage_used <= 0.10 then 1 else 0 end ) as group_a ,
sum( case when fat.percentage_used > 0.10 and fat.percentage_used < 0.50 then 1 else 0 end ) as group_b ,
sum( case when fat.percentage_used >= 0.50 and fat.percentage_used < 1.00 then 1 else 0 end ) as group_c ,
sum( case when fat.percentage_used >= 1.00 then 1 else 0 end ) as group_d ,
sum( case when fat.percentage_used is null then 1 else 0 end ) as group_e
from fact_table fat
join groups fts on tfs.dim_project_id = fat.dim_project_id
group by fat.building_id
) t
join fact_table bn on bn.building_id = t.building_id

Answer 2

Instead of putting the aggregate as the THEN, wrap the CASE statement in an aggregate:
SELECT
SUM(CAST(FTS.GROUP_A AS BIGINT)) AS GROUP_A,
SUM(CAST(FTS.GROUP_B AS BIGINT)) AS GROUP_B,
SUM(CAST(FTS.GROUP_C AS BIGINT)) AS GROUP_C,
SUM(CASE WHEN FAT.PERCENTAGE_USED <= '0.10' THEN 1 ELSE 0 END) AS PROJECTS_L10,
SUM(CASE WHEN FAT.PERCENTAGE_USED >= '0.50' THEN 1 ELSE 0 END) AS PROJECTS_G50,
SUM(CASE WHEN FAT.PERCENTAGE_USED >= '1.00' THEN 1 ELSE 0 END) AS PROJECTS_G100,
DAYS(DATE('2014-07-01')) - DAYS(CURRENT DATE) AS DAYS_LEFT,
(DAYS(DATE('2014-07-01')) - DAYS(CURRENT DATE))/7 AS WEEKS_LEFT,
DAYS(DATE('2013-12-31')) - DAYS(CURRENT DATE) AS DAYS_LEFT_YEAR
FROM FACT_TABLE AS FAT
INNER JOIN GROUPS AS FTS ON FAT.DIM_PROJECT_ID = FTS.DIM_PROJECT_ID
GROUP BY FAT.DIM_BUILDING_ID, FAT.BUILDING_NAME;
The ELSE 0 isn't needed, but some like to see it in the query.
Alternatively this should work as well:
COUNT(CASE WHEN FAT.PERCENTAGE_USED >= '0.50' THEN 1 END) AS PROJECTS_G50,