Creating the DDL -- the SQL is the same regardless if the 1 side of the 1:M

Question

is optional or not.
Example:
Entity STUDENT has Student_ID as UID and a Student_Name. Entity LOCKER has LOCKER_ID as its UID and a location.
I created a sample 1:M relation between STUDENT and LOCKER where each STUDENT may have zero or more LOCKERs and each LOCKER may be owned by one STUDENT.
The logical model in the data modeler looks like this: STUDENT - - - - - <-LOCKER.
The DDL generation in the data modeler created this SQL:
CREATE TABLE Locker
LockerID NUMBER NOT NULL ,
LockerLocation VARCHAR2 ,
Student_ID NUMBER
ALTER TABLE Locker
ADD CONSTRAINT Locker_PK PRIMARY KEY ( LockerID ) ;
CREATE TABLE Student
Student_ID NUMBER NOT NULL ,
StudentName VARCHAR2 (20)
ALTER TABLE Student
ADD CONSTRAINT Student_PK PRIMARY KEY ( Student_ID ) ;
ALTER TABLE Locker
ADD CONSTRAINT Relation_6 FOREIGN KEY
Student_ID
REFERENCES Student
Student_ID
ON DELETE SET NULL
I modified the relationship so that each STUDENT MUST have one or more LOCKERs so the logical model now looks like this: STUDENT--- - - - <- LOCKER but the DDL generated the exact same SQL.
Is this correct or did I forget something in the model?
Edited by: user2014134 on Jan 16, 2011 11:37 PM

Answer 1

I tried both version 2 and version 3 of the Oracle data modeler with the same results.
I'm using the Barker notation for the logical model in case you were thinking that was an arrow pointing to student -- it's actually crow's feet.
The logical model looks like this when the relationship is not mandatory (e.g. a student may or may not have one or more lockers)
STUDENT - - - - - - - - - - <- LOCKER
and the logical model looks like this when the relationship is mandatory (e.g. a student must have one or more lockers)
STUDENT -- (solid line) -- - - - - - - - - - <- LOCKER
Should I expect the relational model to be different for both of these? And the DDL as well? The data modeler is showing me the same thing for either (in versions 2 and 3).