Nested SPARQL Query - sparql

Question

I have the following structure an Object and each Object has multiple Children as Changelog to the Parent Object and each Change Log has an Author.
Now each Changelog has status and Timestamp I would now like to write a SPARQL query where I need to get the list of Objects which has me as the author and of particular status say "to be approved" and it has to be the latest changelog.
This query is what I have tried so far :
I try to get first the changelog then the object related to it after that get all the other changelog in it and compare the latest changelog by timestamp and filter it if it is greater.
select ?Object WHERE{ ?author myPrefix:userId "myuserid".
?changelog myPrefix:hasApprover ?author .
?changelog myPrefix:timestamp ?dv
FILTER( ?dv >= ?latestdate )
{
SELECT (max(?dv1) AS ?latestdate) WHERE {
?Object myPrefix:hasChangeLog ?changelog .
?Object myPrefix:hasChangeLog ?changelog1 .
?changelog1 myPrefix:timestamp ?dv1 .
}
}
?changelog myPrefix:status "To be approved" .
?Object myPrefix:hasChangeLog ?changelog .}
What I am doing wrong here is that it compares it to all the Objects changelog and not Objectwise comparison how can I achieve that?

Answer 1

As per the suggestion from UninformedUser:
select ?Object WHERE{ ?author myPrefix:userId "myuserid".
?changelog myPrefix:hasApprover ?author .
?changelog myPrefix:timestamp ?dv
FILTER( ?dv >= ?latestdate )
{
SELECT (max(?dv1) AS ?latestdate) WHERE {
?Object myPrefix:hasChangeLog ?changelog1 .
?changelog1 myPrefix:timestamp ?dv1 .
}group by ?Object
}
?changelog myPrefix:status "To be approved" .
?Object myPrefix:hasChangeLog ?changelog .}