Utilisez DSL.trunc(Field, DatePart)
, c'est-à-dire
Result<Record1<Timestamp>> result = createQueryBuilder()
.selectDistinct(trunc(incomeTable.REF_DATE, DatePart.DAY).as("refdate"))
.from(incomeTable)
.where(incomeTable.PROBOS_ID.eq(probosId))
.fetch();