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<blockquote>
So the third table will have primary keys of both the source tables in the this case StudentId and TeacherId, now the subjectId defines which subject the teacher is taught &nbsp;the student. Another important column is Year. Which year they are learning that subject.<br />
<br />
For Subject table we can have SubjectId, SubjectName...startingyear<wbr />..etc as columns..
</blockquote>
<br />
is subjectid is primary key in this new third table?<br />
<br />

<blockquote>
So for this example the third table will be StudentTeacher(StudentTeac<wbr />herId , StudentId, TeacherId, SubjectId , Year ) 
</blockquote>
is StudentTeacherId is primary key in this new third table?<br />
<br />
how this third table makes DMLs smooth to insert , select etc?
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<div>
<blockquote>
&gt;&gt;is subjectid is primary key in this new third table?<br />
No
</blockquote>
<br />
is it just regular column if not primary key column?<br />
any end to end example or link or resource to understand this DML operation using probably some java code as i am a java guy?<br />
<br />
any good free video tutorials on this to comprehend better?
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<div>
Are you clear about 1:n relationships? If not, the key to understanding n:m is first understanding 1:n relations.<br />
<br />
The need is clear from the outset: Starting with two tables any of them can only have one foreign key, which only points to one other record. Foreign keys on both tables also can't solve the problem. <br />
<br />
What do you need? You need to store pairs of keys, as many as there are relations, not only from this record to another one, but from any to any record. The only way to easily do that is to store those key pairs in a separate table. That way the n:m relation is split into two n:1 and 1:m relations.<br />
<br />
Bye, Olaf.
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Split points evenly across all posts that added to the conversation (eg first post picked as best and all other contributory posts marked as assisted).
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<div class="content wysiwyg-content">
why we need junction table for many to many.<br />
<br />
i am not clear on that concept. can you please elaborate with example tables with data?<br />
i am going through below link but not completely clear<br />
<a href="https://www.youtube.com/watch?v=P_nhBKs25DQ" rel="ugc">https://www.youtube.com/watch?v=P_nhBKs25DQ</a><br />
please advise
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why we need junction table for many to many.

i am not clear on that concept. can you please elaborate with example tables with data?
i am going through below link but not completely clear
https://www.youtube.com/watch?v=P_nhBKs25DQ
please advise

junction/bridge table for many to many.

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