SQL。如何引用复合主键Oracle？

ConSTRAINT fk_column
FOREIGN KEY (column1, column2, … column_n)
REFERENCES parent_table (column1, column2, … column_n)

在你的情况下

create table Visit_Treat (TreatCode CHAr(6) constraint cTreatCodeFK references Treatment(TreatCode),SlotNum NUMBER(2),DateVisit DATE,constraint cVisitTreatPK primary key (SlotNum, TreatCode, DateVisit),constraint fk_slotnumDatevisit FOREIGN KEY(SlotNum,DateVisit) references Visit(SlotNum,DateVisit));