HQL:
Select distinct (sourceAlias) From A as sourceAlias join sourceAlias.refCollection as newAlias where newAlias.id is not null

Here in the above query newAlias.id returns a composite primary key, hence the sql is
select ...... where(pk1,pk2) is not null
ERROR util.JDBCExceptionReporter - Operand should contain 1 column(s)

how can we convert into HQL which is equivalent to SQL
select .... where(pk1 not null, pk2 not null)

Have you managed to solve this? I am curious about this too, tks!