Meaning of 1:1, 1:1 generalization, 1:n, 1:n non identifying, n:m

[Joshua Beall]

Hi All,

I've been taking a look at DB Designer 4, and looking through the
documentation (http://www.fabforce.net/dbdesigner4/doc/index.html) I am a
little unclear on some of their nomenclature:

'1:1' - Ok, one to one. Got it.
'1:1' generalization - Don't know this. Obviously different somehow from
one to one, but how?
'1:n' - One to many, I assume.
'1:n non identifying' - Nonidentifying? What does this mean?
'n:m' - Many to many? Again, not sure.

Can anyone help clarify?

Thanks!
-Josh

[GH]

weird... about 1:! generalization and 1:m non identifying...

I think that these examples can make it better to understand some of
those terms... I am quoting from Database Systems -- Design,
Implementation & Management fouth edition by Rob & Coronel (page 23)

Conceptual Modules use three types of relationships to descrive
associates amond data: one-to-many, many-to-many, and one-to-one.
Database designers usually use shorthand notations 1:M, M:N, and 1:1
for them, respectfully. The following examples illustrate the
distinctions among the three.

1. *ONE-TO-MANY Relationships* A painter pains many diffrent
paintings, but each one of hem is painted by only that painter. Thus
the painter ("the one") is related to the paintings (the "many").
Therefore, database designers lable the relationship "PAINTER paints
PAINTINGS" as 1:M. Simillarly, a customer account (the "one") might
contain many invoices, but those invoices (the "many") are related to
only a singe customer account. The "CUSTOMER generates INVOICE"
relationship would also be labled 1:M

2 *MANY-TO-MANY Relationship* An employee might learn many job skills,
ans each job skill might be learned by many employees. Database
designers label the relationship "EMPLOYEE learns SKILL" as M:N.
Similarly, a student can take many courses, and each course can be
taken by many students, thus yielding the M:N relationship label for
the relationship for the relationship expressed by "STUDENT takes
COURSE"

3 *ONE-TO-ONE Relationship* A retail company's management structure
may require that eaco one of its stores be managed by a single
employee. In turn, each store manager -- who is an employee -- only
manages a single store. Therefore the relationship "EMPLOYEE manages
STORE" is labled 1:1





Hope that this helps... as per the non identifying and the
generalizations... DUNNO

Post by Joshua Beall
Hi All,
I've been taking a look at DB Designer 4, and looking through the
documentation (http://www.fabforce.net/dbdesigner4/doc/index.html) I am a
'1:1' - Ok, one to one. Got it.
'1:1' generalization - Don't know this. Obviously different somehow from
one to one, but how?
'1:n' - One to many, I assume.
'1:n non identifying' - Nonidentifying? What does this mean?
'n:m' - Many to many? Again, not sure.
Can anyone help clarify?
Thanks!
-Josh
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For list archives: http://lists.mysql.com/mysql

[Donna Hinshaw]

A 1:M (one to many) non-identifying means that the associated record in the
-one- table is not a parent of the associated record in the -many-
table, but
rather just related.

An example:

an identifying 1:M would be a building which has many rooms. The -one- table
carries data about the building .. e.g., street address, number of
floors, name.
The -many- table carries data about the rooms in the building .. e.g.,
room number,
capacity, special characteristics. The room cannot exist without the
building,
therefore this 1:M is an identifying relationship.

a non-identifying 1:M would be a DVD which has many renters. The -one- table
carries data about the DVD... e.g., the movie name, the artist. The
-many- table
carries data about each person who rents that DVD .. e.g., name, price paid.
The DVD can exist on its own, without ever having been rented, and the
person
can exist on her own, without ever having rented any DVD, therefore this 1:M
is a non-identifying relationship.

Donna Hinshaw

Post by GH
weird... about 1:! generalization and 1:m non identifying...
I think that these examples can make it better to understand some of
those terms... I am quoting from Database Systems -- Design,
Implementation & Management fouth edition by Rob & Coronel (page 23)
Conceptual Modules use three types of relationships to descrive
associates amond data: one-to-many, many-to-many, and one-to-one.
Database designers usually use shorthand notations 1:M, M:N, and 1:1
for them, respectfully. The following examples illustrate the
distinctions among the three.
1. *ONE-TO-MANY Relationships* A painter pains many diffrent
paintings, but each one of hem is painted by only that painter. Thus
the painter ("the one") is related to the paintings (the "many").
Therefore, database designers lable the relationship "PAINTER paints
PAINTINGS" as 1:M. Simillarly, a customer account (the "one") might
contain many invoices, but those invoices (the "many") are related to
only a singe customer account. The "CUSTOMER generates INVOICE"
relationship would also be labled 1:M
2 *MANY-TO-MANY Relationship* An employee might learn many job skills,
ans each job skill might be learned by many employees. Database
designers label the relationship "EMPLOYEE learns SKILL" as M:N.
Similarly, a student can take many courses, and each course can be
taken by many students, thus yielding the M:N relationship label for
the relationship for the relationship expressed by "STUDENT takes
COURSE"
3 *ONE-TO-ONE Relationship* A retail company's management structure
may require that eaco one of its stores be managed by a single
employee. In turn, each store manager -- who is an employee -- only
manages a single store. Therefore the relationship "EMPLOYEE manages
STORE" is labled 1:1
Hope that this helps... as per the non identifying and the
generalizations... DUNNO

Post by Joshua Beall
Hi All,
I've been taking a look at DB Designer 4, and looking through the
documentation (http://www.fabforce.net/dbdesigner4/doc/index.html) I am a
'1:1' - Ok, one to one. Got it.
'1:1' generalization - Don't know this. Obviously different somehow from
one to one, but how?
'1:n' - One to many, I assume.
'1:n non identifying' - Nonidentifying? What does this mean?
'n:m' - Many to many? Again, not sure.
Can anyone help clarify?
Thanks!
-Josh
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For list archives: http://lists.mysql.com/mysql