sparql: randomly select one connection for each node

Here is my problem that has been bothering me for many days: I have the following query results:

<node:1><urn:connectTo><node:2>
<node:1><urn:connectTo><node:3>
<node:1><urn:connectTo><node:4>
<node:2><urn:connectTo><node:10>
<node:2><urn:connectTo><node:11>
<node:2><urn:connectTo><node:12>
<node:3><urn:connectTo><node:21>
<node:3><urn:connectTo><node:13>
<node:3><urn:connectTo><node:41>
<node:3><urn:connectTo><node:100>
<node:4><urn:connectTo><node:119>
<node:4><urn:connectTo><node:120>

As you can see: every node has more than one connection. I want to select one connection for each node randomly.

I have failed by trying these solutions: (1)

select ?currentNode ?nextNode
where
{
?currentNode ?p ?nextNode
BIND(RAND() AS ?orderKey)
}
ORDER BY ?orderKey
LIMIT 1

(2)

select ?currentNode SAMPLE(?nextNode) as ?nextNode1
where
{
?currentNode ?p ?nextNode
}
GROUP BY ?currentNode

Note: the result gives the first connection of each node but not randomly

(3)

select ?currentNode ?nextNode (COUNT(?nextNode) AS ?noOfChoices)
where
{
?currentNode ?p ?nextNode
BIND(RAND() AS ?orderKey)
}
GROUP BY ?currentNode
ORDER BY ?orderKey
OFFSET (RAND()*?noOfChoices)
LIMIT 1

They all failed. Could anyone show a right solution to this problem? I really think this is a typical problem in many situations. Thank you!