Query does not give exact results

hi all ,

how r u ???

in My Query .

select top 10  Post.PosTD 
from Post inner join UsersInContact on Post.UserId=UsersInContact.UserId
where UsersInContact.ContactID=10

if i write this query , it give me the First top 10 Post Written By Only One User !! and it should Give Me top 10 Post By different Users not only one user.

assume that this is My Table :

PostID           UserName             PostBody
1                User1                 Hi
2                User2                 Hi
3                User3                 HI
... so on        .... so on            .... so on

when i write above Query :

it give me the First 10 Post Written By User1 only , althougth the top 10 Post Written By Different Users From User1 to User10

this is mean there is some thing wrong with relationship Between two Tabel???

note:

if i Order My Query By Using Order By PostID desc ....it give me Exact Resluts but the query seem to too slowly