SQL Server : WHERE clause case with between - sql

Question

I have a script which I want to extract values from db accordingly with some dates.
I have a function which return a date, this date can be currentDate - 1 month, or can be curentDate -2 months. The function is
set #syssDate = DATEADD(month, -1, #syss_date);
and I have declared a start date:
declare #start_quarter datetime
set #start_quarter = '2015-07-01';
All I want in my WHERE clause to add a
case
when syssDate = start_quarter
then bu.date between '2015-01-01' and '2015-10-01'
else -- another date
My query looks like:
declare #start_quarter datetime
set #start_quarter = '2015-01-01';
declare #actual_Date datetime
set #actual_Date = DATEADD(month, -1, #rollover_date);
select sum(t.Revenue) as Revenue from (
select sum(bu.value) as Revenue
from bus_category_for bu
join bus_category buc on buc.id=bu.bus_category_id
join bus bu on bu.id=buc.bus_id
where buc.type_id=18 and bu.id=21 and
--Here I want to add a case statement
bu.date between '2015-01-01' and '2015-10-01'

Answer 1

I Guess you need something like this
SELECT Sum(t.Revenue) AS Revenue
FROM (SELECT Sum(bu.value) AS Revenue
FROM bus_category_for bu
JOIN bus_category buc
ON buc.id = bu.bus_category_id
JOIN bus bu
ON bu.id = buc.bus_id
WHERE buc.type_id = 18
AND bu.id = 21
AND ( ( #syssDate = #start_quarter
AND bu.date BETWEEN '2015-01-01' AND '2015-10-01' )
OR ( another date ) ))a

Answer 2

Try something like
WHERE (syssDate = start_quarter AND bu.date between '2015-01-01' and '2015-10-01')
OR (yssDate <> start_quarter AND bu.date between '2016-01-01' and '2016-10-01')
Generally, it's advisable not to use between for dates. It's better to use bu.date >= '2015-01-01' AND bu.date < '2015-10-02'. See here.