Beginner: Many to Many Relationships

[Peter]

Hello,

Thanks for reviewing my question. I would like a little
help understanding what I actually do with a junction
table. I understand to create a junction table you take
the primary keys from each of table and put them into the
third table. OK - then what do I do - use the junction
table for my queries? (This is the part I don't
understand.)

Many Thanks
Peter

 

[Allen Browne]

Peter, take at look at this example:
Relationships between Tables (School Grades example)
at:
http://allenbrowne.com/casu-06.html

The example shows how, and why, and how to interface the junction table.

 

[Tim Ferguson]

I would like a little
help understanding what I actually do with a junction
table.

Students
========
Eric
Samantha
George

Classes
=======
Maths
English
Welsh

Attends <----- the "junction" table
=======
Eric Maths
Samantha English
Samantha Welsh
George English
George Welsh

Therefore Eric does only Maths, Samantha takes English and Welsh, and so
does George. This is hugely simplified: in a real world example, the names
would likely be replaced by codes or numbers and there would be extra
fields like
Students(LName, Address, BankAccount);
Classes(DateStart, Cost, ChiefLecturer); and
Attends(RegisteredDate, HasPaid, FinalGrade)
and so on.

Hope that helps


Tim F