Combine SQL Count Results - sql

Question

I'm currently trying to teach myself SQL in order to write better reports with our Orion system and I'm running into a small issue. I want to generate a report with a count of the number of Windows machines and Linux machines. This is my current code.
SELECT OperatingSystem, Count(OperatingSystem) AS TotalMachines
FROM Machines
Where
(
(OperatingSystem LIKE '%Windows%') OR
(OperatingSystem LIKE '%Linux%')
)
GROUP BY OperatingSystem
And the return I get is this
Red Hat Enterprise Linux 20
Novell SUSE Linux Enterprise 17
Debian Linux 5
Windows Server 2008 (32-bit) 11
Windows Server 2008 R2 (32-bit) 49
Windows Server 2008 (64-bit) 33
Windows Server 2008 R2 (64-bits) 16
Windows Server 2003 (32-bit) 35
Is it possible to combine all of the different Linux Operating Systems into a single row called Linux and combine all of the Windows Operating Systems into a single row called Windows in an SQL Query?

Answer 1

Yes. You want to use case in the group by clause itself:
SELECT (case when OperatingSystem LIKE '%Windows%' then 'Windows'
when OperatingSystem LIKE '%Linux%' then 'Linux'
end) as WhichOs, Count(*) AS TotalMachines
FROM Machines
Where (OperatingSystem LIKE '%Windows%') OR
(OperatingSystem LIKE '%Linux%')
GROUP BY (case when OperatingSystem LIKE '%Windows%' then 'Windows'
when OperatingSystem LIKE '%Linux%' then 'Linux
end);
EDIT:
The above should work (note the same expression is in the select and group by. Perhaps this will work:
SELECT WhichOs, Count(*) AS TotalMachines
FROM (SELECT m.*,
(case when OperatingSystem LIKE '%Windows%' then 'Windows'
when OperatingSystem LIKE '%Linux%' then 'Linux'
end) as WhichOs
FROM Machines m
) m
Where (OperatingSystem LIKE '%Windows%') OR
(OperatingSystem LIKE '%Linux%')
GROUP BY WhichOs;

Answer 2

to solve such problems I prefer to use union neither case, as it helps you easily extend query in future:
select OSType, count(*) as TotalMachines
from (
SELECT 'Linux' as OSType FROM Machines WHERE OperatingSystem LIKE '%Linux%'
UNION ALL
SELECT 'Windows' as OSType FROM Machines WHERE OperatingSystem LIKE '%Windows%'
) as subquery
GROUP BY OSType
in any case, check both variants and select fastest

Answer 3

Try something like this:
SELECT
case
when OperatingSystem like '%Windows%' then 'Windows'
when OperatingSystem like '%Linux%' then 'Linux'
else 'Other'
end as Operating_System
, Count(OperatingSystem) AS TotalMachines
FROM Machines
Where
(
(OperatingSystem LIKE '%Windows%') OR
(OperatingSystem LIKE '%Linux%')
)
GROUP BY
OperatingSystem
, case
when OperatingSystem like '%Windows%' then 'Windows'
when OperatingSystem like '%Linux%' then 'Linux'
else 'Other'
end