列中不同值的计数

Question

I have a table like

machine_id      OS
----------      --
1               PC
2               PC
3               MAC
4               UNIX
5               PC

How do I return each OS and the number of times it occurs? I can't group by OS because I would just get a distinct list of OS. I want to know how many times each OS occurs in the column

Answer 1

 select OS, count(*)as TotalForOS
 from table
 group by OS