Since the Zend select is not nice for the jois stuff,
the ActiveRecord offer to add a join string in the fecthall.

The fetchAll function is called with
fetchAll($where = null, $order = null, $count = null, $offset = null, $join = null)
So When you use is, you can specific all of these strings for construct the sql query.

Examples:

$projects = $project->fetchAll(null, null, null, null, 'LEFT JOIN projectuserrolerelation ON projectuserrolerelation.projectId = Project.id');

$projects = $project->fetchAll('Project.id = 1', 'title DESC', null, null, 'LEFT JOIN projectuserrolerelation ON projectuserrolerelation.projectId = Project.id');

The query will return only the fields for the current activerecord table,
and not the fields of the other relations tables.