How do I avoid loading all child records with the actual table

select
  matches.name,
  matches.limit

from (
    select
      c.name,
      c.customerId,
      l.limit,
      l.limitId,
      count(*) over(partition by cc.customerId, lc.limitId) as matchCount
    from tblCustomer c
    join tblCustomerCategory cc on c.customerId = cc.customerId
    join tblLimitCategory lc on cc.categoryId = lc.categoryId
    join tblLimit l on lc.limitId = l.limitId
) as matches

join (
    select
       cc.customerId,
       count(*) as categoryCount
     from tblCustomerCategory cc
     group by cc.customerId
) as customerCategories
on matches.customerId = customerCategories.customerId

join (
    select
      lc.limitId,
      count(*) as categoryCount
    from tblLimitCategory lc
    group by lc.limitId
) as limitCategories
on matches.limitId = limitCategories.limitId

where matches.matchCount = customerCategories.categoryCount
and matches.matchCount = limitCategories.categoryCount

-- relations (record_id, parent_id)
SELECT parents.record_id 
FROM 
    relations parents
    LEFT JOIN relations children
    ON parents.record_id = children.parent_id
WHERE 
    children.record_id IS NULL

public User updateUserDetails(User template){
    User toUpdate = EM.find(User.class,template.getId());
    Set<UserProject> present = template.getUserProjects();//the ones should be kept
    Set<UserProject> toDel = new HashSet<>(toUpdate.getUserProjects());
    toDel.removeAll(present); //the difference so the once should be removed
    Set<UserProjcet> newOnes = new HashSet<>(present);
    newOnes.removeAll(toUpdate.getUserProjects()); //freshly added
    for (UserProject uP : toDel) {
        up.getProject().getUserProjects().remove(uP); //from each project removing reference to UserProject
        toUpdate.getUserProjects().remove(uP);
        EM.remove(uP); //removing the actuall 
    }
    toUpdate.getUserProjects().addAll(newOnes);
    return toUpdate;
}