using find's -path and -prune options

Question

I want to find files in the /tmp directory. I use -path and -prune to exclude the subdirectory sgid from the results.

So I do something like this:

[root@ tmp]# find ./ -path ./sgid -prune -o -name 'foo*'
./sgid
./foo1
./dir1/foo2
./sgid0/foo1
./sgid0/foo
./sgid0/foo2

However the output still contains the sgid subdirectory, which is not what I expect.

But when i do like the following：

[root@ tmp]# find ./ -path ./sgid -prune -o -name 'foo*' -print
./foo1
./dir1/foo2
./sgid0/foo1
./sgid0/foo
./sgid0/foo2

The output matches my expectation. Why does the command have to include the -print option?