I have a two tables named student and exam.a many to many relationship is maintained between the two tables using a link table named studentexam.The table structure is as follows

STUDENT
- studentid
-name


EXAM
-examid
-examname
-year


STUDENTEXAM
-STUDENT_EXAM_ID
-STUDENT_ID
-EXAM_ID
-Grade
-totalmarks

Now i want to autopopulate the STUDENT_EXAM table
whenever some record is entered int the STUDENT and EXAM table

Is there any way in which i can do it?

Kindly help

Thanks...

Fisrt I think you should check your databse design,
if you are looking for a Many-to-Many relation the join table should contain
only two keys STUDENT_ID and EXAM_ID.
STUDENT_EXAM_ID is not necessary since you apply the Unique constraints on both
STUDENT_ID and EXAM_ID.

I don't know wht means for you Grade and total marks so may be I'm wrong...

You need of course two collections on your entty object
Exams on Student class
Students on Exams class

Then the map files should look like these ones

For Student class

<set name="Exams" table="STUDENTEXAM" inverse="true">
<key column="STUDENT_ID"/>
<many-to-many class="Class Exam name,namespace name" column="EXAM_ID"/>
</set>

For Exam class

<set name="Students" table="STUDENTEXAM" cascade="all">
<key column="EXAM_ID"/>
<many-to-many class="Class Student name,namespace name" column="STUDENT_ID"/>
</set>

The token <set /set> is depending of your collection type.
the position of inverse and cascading is up to you depending which "direction" of the relation you want to use.

I suggest you to read the NHibernate doc concerning Many-to-Many and also Hibernate in action Chapter 6.3.2

Tips : It's better if the field name for your key is the same on evry table...


Hope this help you...

Actually, I think you don't have a many to many situation at all. You should have a separate entity called student exams because each student has a grade for each exam they take (I think your totalmarks column is computed and should be part of the student table).

So you have a many-to-one from StudentExam to Student and a Many-to-one from StudentExam to Exam.

I think you don't have a many to many situation at all.

I'm agree STUDENTEXAM should correspond to an entity "Result" with two One-To-Many relations with Exam and Student.

Thanks