Merging rows in SQL - php

Question

My table looks like this:
Dept Wk1 Wk2
100 25 50
200 25 50
300 25 50
400 25 50
500 25 50
My results need to look like this:
Dept Wk1 Wk2
100 25 50
200 25 50
300 25 50
400 50 100
Things worth noting; the database is Pervasive PSQL10 and I'm using PHP to handle the results. I thought about doing this merge in PHP, but ideally if it could be done in the query that would save me the need for the extra code.
Reason for combining rows is that 2 depts will be treated as one when the data is pulled.
I think I'm overthinking it, but I've explored union, group by, and stuff (which I'm probably using incorrectly) and nothing is giving me what I need.
Any help or direction would be greatly appreciated, because what I've read so far addresses rows that have the same values, but not different.
Here is what my query actually looks like:
SELECT
dept_workcenter,
SUM(case when right(date_sequence,2) between 0 and 7 then hours_worked else 0 end) as wk1,
SUM(case when right(date_sequence,2) between 8 and 14 then hours_worked else 0 end) as wk2,
SUM(case when right(date_sequence,2) between 15 and 21 then hours_worked else 0 end) as wk3,
SUM(case when right(date_sequence,2) between 22 and 28 then hours_worked else 0 end) as wk4,
SUM(case when right(date_sequence,2) between 29 and 31 then hours_worked else 0 end) as wk5
FROM job_detail
WHERE job between '017079' AND '017207'
AND date_sequence BETWEEN '141200' and '141231'
AND dept_workcenter != ''
GROUP BY dept_workcenter
HAVING SUM(hours_worked) <> '0'
AND SUM(hours_worked) > '0.05';

Answer 1

You can use a case statement in the group by:
select (case when dept in (400, 500) then 400 else dept end) as dept,
sum(wk1) as wk1, sum(wk2) as wk2
from table t
group by (case when dept in (400, 500) then 400 else dept end)
order by dept;

Answer 2

So basically take the 500 and merge it with the 400?
SELECT Dept, SUM(Wk1) AS Wk1, SUM(Wk2) AS Wk2
FROM yourtable
GROUP BY Dept IN (400,500), Dept

Answer 3

This is not an uncommon problem in reporting. The typical method to handle this is to generate a temporary table in which you can modify the 500 to be 400, and then do a GROUP BY and SUM. This method will become more useful the more complicated your reporting becomes over time.
create table #DeptReptTable from select * from department;
update #DeptReptTable set Dept = 400 where Dept = 500;
select Dept, SUM(Wk1) Wk1, SUM(Wk2) Wk2 from #DeptReptTable group by Dept
drop table #DeptReptTable
Note: The # in front of the temp table is a Sybase-ism, which will create a table tied to the current SQL connection / session. I don't know if that magic works for Pervasive.