Display equation result - sql

Question

I want to display the results of this equation (B/A+B)*100
I dont want rows of stage=1 and state is open
A are the rows where stage=1 and state is lost
B are the rows where stage=2 or higher irrespective of status
------------------------------------
name |stage| state
------------------------------------
| ABC | 1 | open
| DEF | 1 | open
| ABB | 1 | lost
| ABD | 1 | lost
| PQR | 2 | won
| PQF | 3 | lost
| PQY | 4 | open
| PQN | 5 | won
| PQM | 6 | lost
| PQM | 7 | lost
The result should be (6/6+2)*100= 75 %

Answer 1

SELECT
[equation] = CASE
WHEN (ISNULL([a].[cnt], 0) + ISNULL([b].[cnt], 0)) = 0 THEN NULL
ELSE (ISNULL([b].[cnt], 0) / (ISNULL([a].[cnt], 0) + ISNULL([b].[cnt], 0))) * 100
END
FROM
(
SELECT [cnt] = CAST(0 AS MONEY)
) AS [x]
OUTER APPLY
(
SELECT [cnt] = CAST(COUNT(*) AS MONEY) FROM [my_table] WHERE [stage] = 1 AND [state] = 'lost'
) AS [a]
OUTER APPLY
(
SELECT [cnt] = CAST(COUNT(*) AS MONEY) FROM [my_table] WHERE [stage] > 1
) AS [b];

Answer 2

No need for subqueries or outer apply().
select [B/(A+B)]=
(sum(case when stage >1 then 1.0 else 0.0 end)
/
sum(case
when stage =1 and state = 'lost'
then 1.0
when stage > 1
then 1.0
else null
end))*100
from t
test setup: http://rextester.com/THWUY43139
create table t (name char(3), stage int, state varchar(4))
insert into t values
('ABC',1,'open')
, ('DEF',1,'open')
, ('ABB',1,'lost')
, ('ABD',1,'lost')
, ('PQR',2,'won' )
, ('PQF',3,'lost')
, ('PQY',4,'open')
, ('PQN',5,'won' )
, ('PQM',6,'lost')
, ('PQM',7,'lost');
query:
select
[B]=sum(case when stage >1 then 1 else 0 end)
, [(A+B)]=sum(case
when stage =1 and state = 'lost'
then 1
when stage > 1
then 1
else 0
end)
, [B/(A+B)]=(sum(case when stage >1 then 1.0 else 0.0 end)
/
sum(case
when stage =1 and state = 'lost'
then 1.0
when stage > 1
then 1.0
else null
end))*100
from t
results:
+---+-------+----------+
| B | (A+B) | B/(A+B) |
+---+-------+----------+
| 6 | 8 | 75,00000 |
+---+-------+----------+