Merging several joins into a single select / case - tsql

Question

I am currently querying a table 4 times using different criteria and then using left joins as part of a much larger query to return all the data. The larger query does not run particularly quickly and I am fairly certain that my current approach is not efficient.
What I am wondering is if it is possible to somehow use a CASE statement to increment one of the 4 columns. My 4 queries currently are:
SELECT ts.department,
Sum([hours]) AS ChargeableTimeYTD
FROM bwbfiles.sos.timesummary ts
WHERE category = 'C'
AND [year] = '2019'
GROUP BY department
SELECT ts.department,
Sum([hours]) AS ChargeableTimeMTD
FROM bwbfiles.sos.timesummary ts
WHERE category = 'C'
AND [year] = '2019'
AND [period] = 4
GROUP BY department
SELECT ts.department,
Sum([hours]) AS NonChargeableTimeProBono
FROM bwbfiles.sos.timesummary ts
WHERE category = 'NC'
AND ( [act_code] = '001N'
OR [act_code] = '00N6' )
AND [year] = '2019'
GROUP BY department
SELECT ts.department,
Sum([hours]) AS NonChargeableTimeNonProBono
FROM bwbfiles.sos.timesummary ts
WHERE category = 'NC'
AND ( [act_code] <> '001N'
AND [act_code] <> '00N6' )
AND [year] = '2019'
GROUP BY department
The aim would be to end up with a query result with 5 columns
Department, ChargeableTimeYTD, ChargeableTimeMTD, NonChargeableTimeProBono, NonChargeableTimeNonProBono
Or instead of CASE would I remove the group by department from each bit and have a query that produced 3 columns
Department, Hours, Category (where Category is ChargeableTimeYTD/ChargeableTimeMTD etc...etc...) and then pivot that into 5 columns.
Thanks in advance!

Answer 1

This may do what i think you're asking for
SELECT ts.department,
Sum(case when category = 'C' then [hours] else 0 end) AS ChargeableTimeYTD,
Sum(case when category = 'C' and [period] = 4 then [hours] else 0 end) AS ChargeableTimeMTD,
Sum(case when category = 'NC' and ([act_code] = '001N' or [act_code] = '00N6') then [hours] else 0 end) AS NonChargeableTimeProBono,
Sum(case when category = 'NC' and ([act_code] <> '001N' or [act_code] <> '00N6') then [hours] else 0 end) AS NonChargeableTimeNonProBono
FROM bwbfiles.sos.timesummary ts
where [year] = '2019'
and [category] in ('C','NC')
GROUP BY department