Below code fetches the user id’s who approved the PO workflow.
select firstonly workflowtrackingstatustable
join workflowtrackingtable
where workflowtrackingstatustable .ContextRecId == purchtable.recid
&& workflowtrackingtable.TrackingContext == workflowtrackingcontext::WorkItem
&& workflowtrackingtable.TrackingType == workflowtrackingtype::Approval
&& workflowtrackingtable.WorkflowTrackingStatusTable == workflowtrackingstatustable .recid;
{
approvername = workflowtrackingtable.User;
}
Regards