Many to many join

Question

Hello,
Please help me create the many-to-many relationship between these tables that I willl need to do a Master Detail form. The master is tblStandardSheets (PK: ID) the detail is tblSubject (PK: SUBJECTID) and the link is tblLink (PK: RECID, FK: ID, SUBJECTID).
CREATE TABLE "tblStandardSheets"
(     "ID" NUMBER NOT NULL ENABLE,
     "SHEET" VARCHAR2(100),
     "TITLE" VARCHAR2(255),
     CONSTRAINT "tblStandardSheets_PK" PRIMARY KEY ("ID") ENABLE
CREATE OR REPLACE TRIGGER "BI_tblStandardSheets"
before insert on "tblStandardSheets"
for each row
begin
if :NEW."ID" is null then
select "TBLSTANDARDSHEETS_SEQ".nextval into :NEW."ID" from dual;
end if;
end;
ALTER TRIGGER "BI_tblStandardSheets" ENABLE
CREATE TABLE "tblLink"
(     "ID" NUMBER NOT NULL ENABLE,
     "RECID" NUMBER NOT NULL ENABLE,
     "SUBJECTID" NUMBER NOT NULL ENABLE,
     CONSTRAINT "tblLink_PK" PRIMARY KEY ("RECID") ENABLE
ALTER TABLE "tblLink" ADD CONSTRAINT "TBLLINK_FK" FOREIGN KEY ("ID")
     REFERENCES "tblStandardSheets" ("ID") ON DELETE CASCADE ENABLE
ALTER TABLE "tblLink" ADD CONSTRAINT "TBLLINK_FK2" FOREIGN KEY ("SUBJECTID")
     REFERENCES "tblSubject" ("SUBJECTID") ON DELETE CASCADE ENABLE
CREATE OR REPLACE TRIGGER "BI_tblLink"
before insert on "tblLink"
for each row
begin
if :NEW."RECID" is null then
select "TBLLINK_SEQ".nextval into :NEW."RECID" from dual;
end if;
end;
ALTER TRIGGER "BI_tblLink" ENABLE
CREATE TABLE "tblSubject"
(     "SUBJECTID" NUMBER NOT NULL ENABLE,
     "SUBJECT" VARCHAR2(255),
     CONSTRAINT "tblSubject_PK" PRIMARY KEY ("SUBJECTID") ENABLE
CREATE OR REPLACE TRIGGER "BI_tblSubject"
before insert on "tblSubject"
for each row
begin
if :NEW."SUBJECTID" is null then
select "TBLSUBJECT_SEQ".nextval into :NEW."SUBJECTID" from dual;
end if;
end;
ALTER TRIGGER "BI_tblSubject" ENABLE
ALTER TABLE "tblSubject" ADD CONSTRAINT "tblSubject_FK" FOREIGN KEY ("SUBJECTID")
     REFERENCES "tblLink" ("SUBJECTID") ON DELETE CASCADE ENABLE
ORA-02270: no matching unique or primary key for this column-list
Edited by: user6753348 on Mar 31, 2009 1:39 PM

Answer 1

Like this:
  CREATE TABLE "tblStandardSheets"
   (     "ID" NUMBER NOT NULL ENABLE,
     "SHEET" VARCHAR2(100 BYTE),
     "TITLE" VARCHAR2(255 BYTE),
      CONSTRAINT "tblStandardSheets_PK" PRIMARY KEY ("ID")
CREATE OR REPLACE TRIGGER "BI_tblStandardSheets"
before insert on "tblStandardSheets"
for each row
begin
if :NEW."ID" is null then
select "TBLSTANDARDSHEETS_SEQ".nextval into :NEW."ID" from dual;
end if;
end;
ALTER TRIGGER "BI_tblStandardSheets" ENABLE
  CREATE TABLE "tblSubject"
   (     "SUBJECTID" NUMBER NOT NULL ENABLE,
     "SUBJECT" VARCHAR2(255 BYTE),
      CONSTRAINT "tblSubject_PK" PRIMARY KEY ("SUBJECTID")
CREATE OR REPLACE TRIGGER "BI_tblSubject"
before insert on "tblSubject"
for each row
begin
if :NEW."SUBJECTID" is null then
select "TBLSUBJECT_SEQ".nextval into :NEW."SUBJECTID" from dual;
end if;
end;
ALTER TRIGGER "BI_tblSubject" ENABLE
  CREATE TABLE "HR"."tblLink"
   (     "ID" NUMBER NOT NULL ENABLE,
     "RECID" NUMBER NOT NULL ENABLE,
     "SUBJECTID" NUMBER NOT NULL ENABLE,
      CONSTRAINT "tblLink_PK" PRIMARY KEY ("RECID")
      CONSTRAINT "TBLLINK_FK" FOREIGN KEY ("ID")
       REFERENCES "tblStandardSheets" ("ID") ON DELETE CASCADE ENABLE,
      CONSTRAINT "TBLLINK_FK2" FOREIGN KEY ("SUBJECTID")
       REFERENCES "tblSubject" ("SUBJECTID") ON DELETE CASCADE ENABLE
CREATE OR REPLACE TRIGGER "BI_tblLink"
before insert on "tblLink"
for each row
begin
if :NEW."RECID" is null then
select "TBLLINK_SEQ".nextval into :NEW."RECID" from dual;
end if;
end;
ALTER TRIGGER "BI_tblLink" ENABLE
/You have to create the sequences yourself...
HTH
Roel