Sql – Oracle composite primary key / foreign key question

composite-keyoraclesql

I have a composite primary key in 1 table in oracle. I want to create a foreign key for one table entry in my second table that references the composite primary key in the first table. I am getting the error ORA-02256. Any thoughts on how I can enter this?

CREATE TABLE groupspersonx ( 
  personid number, 
  groupid number, 
  CONSTRAINT pk_persongroupid PRIMARY KEY(personid, groupid) 
); 

CREATE TABLE restrictedgroups ( 
  groupid number, 
  name varchar2(50), 
  dateadded date, 
  since date, 
  notes varchar2(1024), 
  CONSTRAINT pk_groupid PRIMARY KEY(groupid), 
  CONSTRAINT fk_persongroup FOREIGN KEY(groupid) REFERENCES groupspersonx(personid, groupid) 
);

Best Answer

The error is because the FOREIGN KEY is one column, but you're trying to supply two columns as the parent. There's no need to tie to the composite key, because the restrictedgroups doesn't have a personid column...

You also have the relationship backwards - use:

CREATE TABLE restrictedgroups ( 
  groupid number, 
  name varchar2(50), 
  dateadded date, 
  since date, 
  notes varchar2(1024), 
  CONSTRAINT pk_groupid PRIMARY KEY(groupid)
);

CREATE TABLE groupspersonx ( 
  personid number, 
  groupid number, 
  CONSTRAINT pk_persongroupid PRIMARY KEY(personid, groupid),
  CONSTRAINT fk_persongroup FOREIGN KEY(groupid) REFERENCES restrictedgroups(groupid) 
);

I would add a foreign key constraint for whatever table the personid would be coming from.

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