SQL sum of two conditional aggregation - sql

Question

So yesterday I learned about conditional aggregation. I'm fairly new to SQL.
Here is my query:
select
Year_CW,
sum(case when col = 0 then 1 else 0 end) as "Total_sampled(Checked)",
sum(case when col = 1 then 1 else 0 end) as "Total_unsampled(Not_Checked)",
sum(case when col = 0 AND col2 = 'accepted' then 1 else 0 end) as "Accepted",
sum(case when col = 0 AND col2 = 'accepted with comments' then 1 else 0 end) as "Accepted with comments",
sum(case when col = 0 AND col2 = 'request for rework' then 1 else 0 end) as "Request for rework",
sum(case when col = 0 AND col2 = 'rejected' then 1 else 0 end) as "Rejected",
sum(case when col = 0 Or col = 1 then 1 else 0 end) as "Total_DS"
from
(select
Year_CW, SAMPLED as col, APPROVAL as col2
from
View_TEST tv) tv
group by
Year_CW
order by
Year_CW desc
I'm basically just calculating some KPIs grouped by week.
Look at the row for "Total_DS". It is essentially the sum of the first two sums, "Total_sampled(Checked)" and "Total_unsampled(Not_Checked)".
Is there a way that I can add the two columns from the first two sums to get the third one instead of trying to get the data all over again? I feel performance wise this would be terrible practice. It doesn't matter for this database but I don't want to learn bad code practice from the start.
Thanks for helping.

Answer 1

You probably won't see a significant performance hit from what you're doing now as you already have all the data available, you're just repeating the case evaluation.
But you can't refer to the column aliases for the first two columns within the same level of query.
If you can't do a simple count as #Zeki suggested because you aren't sure if there might be values other than zero and one (though this looks rather like a binary true/false equivalent, so there may well be a check constraint limiting you to those values), or if you're just more interested in a more general case, you can use an inline view as #jarhl suggested:
select Year_CW,
"Total_sampled(Checked)",
"Total_unsampled(Not_Checked)",
"Accepted",
"Accepted with comments",
"Request for rework",
"Rejected",
"Total_sampled(Checked)" + "Total_unsampled(Not_Checked)" as "Total_DS"
from (
select Year_CW,
sum(case when col = 0 then 1 else 0 end) as "Total_sampled(Checked)",
sum(case when col = 1 then 1 else 0 end) as "Total_unsampled(Not_Checked)",
sum(case when col = 0 AND col2 = 'accepted' then 1 else 0 end) as "Accepted",
sum(case when col = 0 AND col2 = 'accepted with comments' then 1 else 0 end)
as "Accepted with comments",
sum(case when col = 0 AND col2 = 'request for rework' then 1 else 0 end)
as "Request for rework",
sum(case when col = 0 AND col2 = 'rejected' then 1 else 0 end) as "Rejected"
from (
select Year_CW, SAMPLED as col, APPROVAL as col2
from View_TEST tv
) tv
group by Year_CW
)
order by Year_CW desc;
The inner query gets the data and calculates the conditional aggregate values. The outer query just gets those values from the inner query, and also adds the Total_DS column to the result set by adding together the rwo values from the inner query.
You should generally avoid quoted identifiers, and if you really need them in your result set you should apply them at the last possible moment - so use unquoted identifiers in the inner query, and give them qupted aliases in the outer query. And personally if the point of a query is to count things, I prefer to use a conditional count over a conditional sum. I'm also not sure why you already have a subquery against your view, which just changes the column names and makes the main query slightly more obscure. So I might do this as:
select year_cw,
total_sampled_checked as "Total_sampled(Checked)",
total_unsampled_not_checked as "Total_unsampled(Not_Checked)",
accepted as "Accepted",
accepted_with_comments as "Accepted with comments",
request_for_rework as "Request for rework",
rejected as "Rejected",
total_sampled_checked + total_unsampled_not_checked as "Total_DS"
from (
select year_cw,
count(case when sampled = 0 then 1 end) as total_sampled_checked,
count(case when sampled = 1 then 1 end) as total_unsampled_not_checked,
count(case when sampled = 0 and approval = 'accepted' then 1 end) as accepted,
count(case when sampled = 0 and approval = 'accepted with comments' then 1 end)
as accepted_with_comments,
count(case when sampled = 0 and approval = 'request for rework' then 1 end)
as request_for_rework,
count(case when sampled = 0 and approval = 'rejected' then 1 end) as rejected
from view_test
group by year_cw
)
order by year_cw desc;
Note that in the case expression, then 1 can be then <anything that isn't null>, so you could do then sampled or whatever. I've left out the implicit else null. As count() ignores nulls, all the case expression has to do is evaluate to any not-null value for the rows you want to include in the count.

Answer 2

You can try below
select Year_CW,
sum(case when col = 0 then 1 else 0 end) as "Total_sampled(Checked)",
sum(case when col = 1 then 1 else 0 end) as "Total_unsampled(Not_Checked)",
sum(case when col = 0 AND col2 = 'accepted' then 1 else 0 end) as "Accepted",
sum(case when col = 0 AND col2 = 'accepted with comments' then 1 else 0 end) as "Accepted with comments",
sum(case when col = 0 AND col2 = 'request for rework' then 1 else 0 end) as "Request for rework",
sum(case when col = 0 AND col2 = 'rejected' then 1 else 0 end) as "Rejected",
sum(sum(case when col = 0 then 1 else 0 end) = 0 Or sum(case when col = 1 then 1 else 0 end) = 1 then 1 else 0 end) as "Total_DS"
from (select Year_CW, SAMPLED as col, APPROVAL as col2
from View_TEST tv
) tv
group by Year_CW
order by Year_CW desc