SQL query: How to retrieve the values of a column which are not located on both hosts

I have a studynumber and a studyhost.

I also have a table view which combines the 2 in a nice view. But to really get to the studyhost a few joins are needed. So this is what i want. From that view I need to know which studynumbers are located in 1 of the 2 hosts.

Every studynumber is duplicate stored on 2 separate hosts, one the storage other the mirror.

So we have s1 and m1, s2 and m2, s3 and m3

The study number should be located on both s and m host.

Now i seek a way to find out which studynumbers are located on only the m hosts and not on s hosts and visa versa.

SO i can make a select * from statement but I cannot say where studynumber = 123 and where studynumber is on host m and host s.

Any assistance is greatly appreciated.