cardinality

[Urnen]

I am trying to make the cardinality ((1:1, 1:N, N:M) )) shown in the relations overvieuw in Ms Access.

but i can't find a way to do this, can somebody please tell me how to do that?

or atleast tell me it's not possible at all,

Thx already!

Urn

 

[RoyVidar]

As with most databases, Access can't implement N:M relationship, you'll need the usual workaround using a junction table.

I'm not sure what your question really is, but here's a short treaty on how the relationship interface determines relationships thread700-986818.

Did you just forget to check the "enforce referential integrity" option when creating your relationships?

Roy-Vidar

 

[BNPMike]

In a relational database you create relationships by populating fields and then issuing SQL. If the join fields each have unique values then your relationship is 1:1. If one has multiple values (eg a foreign key) you have 1:n. If both have multiple values you have m:n. I do have tables with the latter but almost always this is not helpful, so you use intersection entities as Urn has said.

The important thing to understand is you do not create these relationships by Access relationships. Access relationships are a mechanism to a) help certain wizards and Front-end processes (eg the QBE Designer), and b) enforce constraints. It is a fundemental rule of the relational model that data and relationships are exclusively represented by table values. No under-the-covers shenanigans are allowed. Access obey this rule.

 

[willir]

Urnen

This is really interesting stuff, and can I ask what you want to do with cardinal numbers? And are you looking at the sequencing of numbers, infinite / finite number sets??

The above posts are correct that establishing relationship will be tricky, and it would help to know your expected outcomes to provide more details.

 

[BNPMike]

A common use of cardinality is as Urnen has used it ie the numbers n and m on each side of the n:m.