DISTINCT ON() in jOOQ

This is definitely non-obvious to discover. There's a SelectDistinctOnStep.distinctOn() method after you've selected your actual columns. The reason why it's non-obvious to discover is that the PostgreSQL syntax itself is a bit hard to model in an internal DSL like jOOQ's.

Think of it this way: You're selecting a set of columns (the correlated subquery) while specifying on which columns a distinctness filter should be applied:

Result<Record> result = create  .select(field("(select nr_zew from bo_get_sip_cti_polaczenie_info(uuid))").as("nr_zew"))  .distinctOn(field("uuid"))  .from("bo_sip_cti_event_day")  .where("data_ins::date = current_date")  .and("kierunek like 'P'")  .and("(hangup_cause like 'NO_ANSWER' or hangup_cause like 'NO_USER_RESPONSE') ")  .fetch();

Or, if you were using the code generator:

Result<Record> result = create  .select(field(     select(BO_GET_SIP_CTI_POLACZENIE_INFO.NR_ZEW)    .from(BO_GET_SIP_CTI_POLACZENIE_INFO.call(BO_SIP_CTI_EVENT_DAY.UUID))).as("nr_zew"))  .distinctOn(BO_SIP_CTI_EVENT_DAY.UUID)  .from(BO_SIP_CTI_EVENT_DAY)  .where(BO_SIP_CTI_EVENT_DAY.cast(Date.class).eq(currentDate()))  .and(BO_SIP_CTI_EVENT_DAY.KIERUNEK.like("P"))  .and(BO_SIP_CTI_EVENT_DAY.HANGUP_CAUSE.like("NO_ANSWER")    .or(BO_SIP_CTI_EVENT_DAY.HANGUP_CAUSE.like("NO_USER_RESPONSE")))  .fetch();

Side-note on your usage of LIKE

Do note that the underscore (_) character is a single-character wild-card in SQL, so your LIKE predicates might not be entirely correct. Ideally, just use ordinary comparison predicates, such as:

• kierunek = 'P'
• hangup_cause IN ('NO_ANSWER', 'NO_USER_RESPONSE')

You don't really seem to need LIKE.