sort by nullable property in a n:1 relation - sorting

Question

I have the following problem - given just a snippet of the whole domain environment, I'll try to explain it:
I have these two domain classes and want to get a list of studies and sort them by the name of their (current) physician. My problem is, that I don´t know how to do the criteria query with gorm...
class Study {
Date studydate
String comment
static belongsTo = [currentPatient:Patient, originalPatient: Patient, originalPhysician: Physician, currentPhysician: Physician]
static mapping = {
columns{
currentPatient column:'id_patient_current'
originalPatient column:'id_patient'
originalPhysician column:'id_physician'
currentPhysician column:'id_physician_current'
}
}
}
class Physician {
String personname
static hasMany = [currentStudies: Study, originalStudies: Study]
static mappedBy = [currentStudies: 'currentPhysician',
originalStudies: 'originalPhysician']
}
and now the query:
def physician = Physician.get(params?.phId)
def studies = Study.withCriteria{
and{
maxResults(limit as Integer)
firstResult(offset as Integer)
currentPhysician{
if(physician){
eq('id', physician.id)
}
order('personname', 'asc')
}
}
}
the problem is that not every study must have a physician - it is possible, that the columns (in the database) - "id_physician" and "id_physician_current" - contain NULL values (the patient did not came from a physician).
via direct sql the query is no problem:
select st.id, ph.personname from study as st left join Physician as ph on ph.ID = st.ID_Physician_Current order by ph.PersonName
I am using grails 1.3.7 on a mssql database

Answer 1

I believe the following query accomplishes what you are asking for.
def studies = Study.withCriteria{
maxResults(limit as Integer)
firstResult(offset as Integer)
order('currentPhysician.personname', 'asc')
if(physician) {
or {
eq('currentPhysician', physician)
isNull('currentPhysician')
}
}
order('currentPhysician.personname', 'asc')
}
Maybe not the exact same sql as you expected but if you are worried about that you shouldn't be writing criteria.