How to get only incoming edges on mySQL graph?

How to get only incoming edges on mySQL graph?

I have a Graph represented on a mySQL table as:
uidFrom, uidTo
1 4
4 1
1 5
5 1
6 1 <- only incoming edge
How to get only the "6, 1" pair, having only "1" as input? I mean, how to
query the only incoming edges to node "1" (not both incoming and outgoing
like 4 or 5)?
Thanks in advance;