Show formula result applying on more than one column - sql

Question

I am on Microsoft SQL Server 2017.
I am having these results on SQL Server applying a simple SELECT sentence:
SELECT Result, Year, Month FROM Table;
Result Year Month
DELAY 2019 5
DELAY 2019 1
PUNCTUAL 2020 2
PUNCTUAL 2020 2
PUNCTUAL 2020 3
PUNCTUAL 2020 3
PUNCTUAL 2020 3
PUNCTUAL 2020 3
DELAY 2020 3
PUNCTUAL 2020 3
I need to get the percentage of PUNCTUAL results, separated by month and year columns. The formula would be the sum of total results separated by month and year, divided by the PUNCTUAL results multiplied * 100.
For instance, on March 2020 would be: 5 punctual / 6 results * 100 = 83.3% punctual results; the other rest are delays, which I am not interested in.
I tried with COUNT CASE WHEN but I couldn't get it to work properly.
For instance, the result I need to get would be like:
Year Month Success
2019 1 0%
2019 5 0%
2020 2 100%
2020 3 83.3%
Thanks for your help.

Answer 1

I like using AVG() for this:
select year, month,
avg(case when result = 'PUNCTUAL' then 1.0 else 0 end) as punctual_rate
from t
group by year, month
order by year, month;
If you want a number between 0 and 100, just use 100.0 rather than 1.0.

Answer 2

You may use the following statement to calculate the percentage using COUNT() and CASE:
SELECT
Year,
Month,
COUNT(CASE WHEN Result = 'PUNCTUAL' THEN 1 END) * 100.0 / COUNT(*) As Success
FROM (VALUES
('DELAY', 2019, 5),
('DELAY', 2019, 1),
('PUNCTUAL', 2020, 2),
('PUNCTUAL', 2020, 2),
('PUNCTUAL', 2020, 3),
('PUNCTUAL', 2020, 3),
('PUNCTUAL', 2020, 3),
('PUNCTUAL', 2020, 3),
('DELAY', 2020, 3),
('PUNCTUAL', 2020, 3)
) v (Result, Year, Month)
GROUP BY Year, Month
ORDER BY Year, Month
Result:
Year Month Success
2019 1 0.000000000000
2019 5 0.000000000000
2020 2 100.000000000000
2020 3 83.333333333333
If you need to get the percentage as text, you may use CONCAT():
CONCAT(
CONVERT(numeric(10, 2), COUNT(CASE WHEN Result = 'PUNCTUAL' THEN 1 END) * 100.0 / COUNT(*)),
'%') AS SuccessFormatted

Answer 3

You can use the aggregation with the FORMAT command to get your desired result:
CREATE TABLE #T1(Result varchar(10),Year int, Month int)
INSERT INTO #T1 VALUES('DELAY', 2019, 5),
('DELAY',2019,1),
('PUNCTUAL',2020,2),
('PUNCTUAL',2020,2),
('PUNCTUAL',2020,3),
('PUNCTUAL',2020,3),
('PUNCTUAL',2020,3),
('PUNCTUAL',2020,3),
('DELAY',2020,3),
('PUNCTUAL',2020,3)
SELECT [Year], [Month], FORMAT( (((PuncCnt * 1.0) / Total)) ,'P2') Success
FROM
(
SELECT [Year],[Month], SUM(CASE WHEN Result = 'PUNCTUAL' THEN 1 ELSE 0 END) PuncCnt, COUNT(*) Total
FROM #t1
GROUP BY [Year],[Month]
) T2
ORDER BY [Year],[Month]
RESULT:
Year Month Success
2019 1 0.00%
2019 5 0.00%
2020 2 100.00%
2020 3 83.33%