how can i make "many to many" Relationship

[Hany Freedom]

I know the idea of "many to many" Relationship but I want anyone give example to me by photo or access file about the "many to many" Relationship .
and thanks

 

[rsmonkey]

http://www.cs.jcu.edu.au/Subjects/cp1500/1998/Lecture_Notes/er_model/f2-2c.gif

just google it there are plenty of examples. Just so you know many to many are bad & portrays bad db design.

 

[Rabbie]

http://www.cs.jcu.edu.au/Subjects/cp1500/1998/Lecture_Notes/er_model/f2-2c.gif

just google it there are plenty of examples. Just so you know many to many are bad & portrays bad db design.

Not always bad design. There are cases where they are necessary. A book can have more than 1 author and an author can have more than 1 book.

Use a junction table to model this realtionship. This will give you 2 1tomany relationships.

HTH

 

[rsmonkey]

you contradict yourself many to many relationships are bad hence having to create a junction table in order to make it into a one to many relationship.

 

[boblarson]

you contradict yourself many to many relationships are bad hence having to create a junction table in order to make it into a one to many relationship.

Negative, he didn't contradict himself. What he did do is to make it possible to create. A junction table is the only way to do this and each side becomes a one-to-many because it can be broken down into two one-to-many relationships.

Many to many is something that isn't bad, it is just that it is possible that they may occur but there aren't many ways to deal with them.

 

[neileg]

Relationships don't exist in Access, they exist in the real world. All you do in Access is model the real world. A many to many isn't good or bad, it exists or it doesn't.

I would observe, however, that a one to one relationship in a database may well indicate bad design. Usually all the data should be in one table. There are exceptions, of course, such as applying security to only some data, or preventing excess network traffic.

 

[Hany Freedom]

all what I want that access file (mdb ,or accdb) that contain simple example about many to many relationship , and thanks.

 

[Pat Hartman]

Take a look at the Northwinds sample that ships with Access. Order details is an example of a junction table. It creates a relationship between Orders and Products.

Your tag line says that you are an Oracle developer - Access is no different from Oracle or any other RDBMS in how it protrays many-to-many relationships.