Modeling a many-to-many relationship in a dimension

Hi, I'm using AWM and I need to create a book dimension which aggregates books about their authors.
My table is: BRIDGE_TABLE_BOOKS(book_key, author_key)
Its data are for example:
Book - Author
1 - 1
1 - 2
2 - 1
3 - 2
4 - 1
4 - 2
5 - 1
because a book can be written by 1 or more authors.
I'd like that AWM could aggregate them through authors as follows:
1
->1
->2
->4
->5
2
->1
->3
->4
is it possibile in AWM?

many-to-many relationships are always represented as fact tables in a dimensional model (Kimball likes the idea of the "bridge" table...but in my opinion a bridge table is nothing more than a 2 dimensional fact table). Doesn't matter whether you're using relational or OLAP, works the same either way.
Simply create a cube dimensioned by book and author. Have a character or boolean measure with Y/N or true/false. Insert tuples where a given book was written by a given author. This is one area where relational is better - don't have to have a dummy measure, just make a "factless fact table" (you can do this in Oracle OLAP also...but it's gotten to the point where Oracle has tried to hide all the complexity of the OLAP language. Unfortunately, that hides a lot of power also...)
What type of reports are you trying to get out?
Thx,
Scott

Similar Messages

Modeling a Many to Many relationship

How can I modeling a Many to Many relationship between a fact table and a dimensión in Essbase?
For example I have a economic zone dimension and a record in the fact is just related to one country... but a country is related to many economic zone...
Is this posible?
Thanks.

Glenn kibbitzes (sp?) on my answers, so it's payback time. :)
There are a couple of ways to approach this:
1) Shared hierarchies: Create a master hierarchy that contains all of your regions/countries/states/provinces/parishes/principalities. Call this one Total. Create separate, nonconsolidating hierarchies like Atlantic, Pacific, etc., and use Essbase's shared members functionality to get those totals.
2) Put two (or more) attribute dimensions against your Geography dimension and assign the base members (Mexico, Brazil, etc.) to attribute dimensions like Atlantic or Pacific. These would be one member attribute dimensions.
3) Use a UDA to do much the same as #2, but with poorer reporting capabilities.
Regards,
Cameron Lackpour
Edited by: CL on Jul 18, 2009 6:33 PM
Owned by Glenn when he pointed out my mistake with approach #2. Oh, the humiliation. But now it's fixed. Never tangle with an Oracle Ace -- your ego will be handed to you, in a nicely wrapped box, with a pretty bow to make the pain go away.

How to model a Many-to-Many relationship in java?

Folks,
I'm having trouble understanding how to properly model a many to many relationship in OO/Java.
The full scenario is in this thread... http://forum.java.sun.com/thread.jspa?threadID=5288115&start=0&tstart=0 it's a college/uni assignment to build a short-course management application. I'm doing the assignment for my own edification.
The scenario (as I see it) is:
* A college offers many Subject's in each of 4 semesters per year.
* A SubjectOffering is identified by the combination of String subjectName, int year, and int semester [1..4]
... each SubjectOffering has a teacher, a cost, a price, etc, etc.
... it models "a running of a named subject"
... for example: "Geography 101 in the first semester of 2007 with Mrs Mappit"
* A Student is identified by String name.
* A Student can enroll in many SubjectOffering's [per semester].
* A Subject has many pupils [per semester].
In my current design:
1. Each Student has a List<Subject> enrollments... of all the subjects they where/are/willbe enrolled in; and
2. Each Subject has a List<Student> pupils... who are enrolled in that subject-offering.
I think I've got an inherent catch 22 here...
1. The student must exist in order to be enrolled in a course;
2. but the course must first exist in for the student to enroll in it.
So which comes first the chicken or the egg? And how?
Coming from a database background, I'm thinking that I really need an enrollments table... that is a List<Enrollment> where an Enrollment object just correlates a Student to a SubjectOffering... modeling: "John Doe did Geography 101 in the first semester of 2007"... that way both the Student and the SubjectOffering can exist independantly of there enrollments/pupils.
But I've got a nagging feeling that there's something basic that I'm just not getting, because I've spent too long in a static C/DB world.
Please can anyone put me straight on the "proper OO way" to do this?
Thanking you, Keith

an Enrollment object just correlates a Student to a SubjectOffering...Sounds like a good plan to me.
Example (Groovy):
class Student {
    String name
    String toString() { name }
class SubjectOffering {
    String name
    String toString() { name }
class Enrollment {
    Student student
    SubjectOffering subject
    String toString() { "$student :: $subject" }
registry = [
    new Enrollment(student:new Student(name:'yawmark'), subject:new SubjectOffering(name:'Biology 101'))
   ,new Enrollment(student:new Student(name:'corlettk'), subject:new SubjectOffering(name:'Chemistry 302'))
   ,new Enrollment(student:new Student(name:'corlettk'), subject:new SubjectOffering(name:'History 204'))
keithSchedule = registry.findAll { it?.student?.name == 'corlettk' }
keithSchedule.each { println it }Output:
corlettk :: Chemistry 302
corlettk :: History 204~

Many to Many Relationships in ejb.....Urgent Pls help

hi all,
Am working in EJB.Now we are coding for many to many relationship.
Company and Salary register
One Company can have many salary register and More than one company can have one salary register
Companyand Salary register are the two tables having details of it.And the intermediate table having pk of company and salary register is Company_salary_register table,I want to add the value in this table having seperate interface.
How to model it? I have given the add method of this company_salary_register table in company bean.I am getting the value of this one as collection.But it is asking me to add the values as the instance of LocalSalary(interfaceand entitybean).If i type cast it as Local Salary Class castexception occurs
Please help me.Even Material of Modelling Many to Many relationship in EJB is enough.
thanx in advance,

THaaaaaanks alottt for the quick reply...
I used the first way to insert the document and i was successful...
but thing is that..
when i do
SQL>desc message_type
message_type is NOT FINAL
Name Null? Type
SYS_XDBPD$ XDB.XDB$RAW_LIST_T
to VARCHAR2(4000 CHAR)
from VARCHAR2(4000 CHAR)
subject VARCHAR2(4000 CHAR)
body VARCHAR2(4000 CHAR)
i can see the structure...
and when i
select count(*) from messages
it says count is 1.
so how to know where the data is ..like below in the data :
'to' it has '[email protected]'
and for 'from' it has '[email protected]'..and so on..
<message>
<to>[email protected]</to>
<from>[email protected]</from>
<subject>Question</subject>
<body>Does this demo work?</body>
</message>
so what is the command to get that data...
because when i do
select * from message_type..it says
select * from message_type
ERROR at line 1:
ORA-04044: procedure, function, package, or type is not allowed here
Plss help me outt.......this will be my final step...
Thankssssssssssssssss

Many to many relationship mapping.

Hi
I have a basic question on how to create a good java class model (POJOs) based on the database model.
I Have to follwing tables
Table1 with columns as
ID1
name
description
Table2 with columns as
ID2
dateCreated ..etc.
Since there is a many to many relationship between table1 and table2
So to map that we have a table3 with columns
ID3
ID1 // fk table1
ID2 // fk table2
browserName
startTime
endTime
So when I create Java classes:
// corresponding to table 1
Class MyTable1
private Integer ID1;
private List ID2; // to map with the table2
// corresponding to table 2
Class MyTable2
private Integer ID2
private List ID1; // to map with table 1
In this way I can create my classes. Is this the best way to put it together.
And where to put the attributed specific to table3. Like the BrowserName and the StartTime and the EndTime.
Any suggestion please.
Thanks.

Your names leave a lot to be desired. Let's start with an example. Suppose I have a problem involving employees and the tasks assigned to them. An employee may have any number of tasks assigned to them and a task can be assigned to any number of employees. The assignment itself has more attributes: when it was assigned, its priority and so on.
public interface Employee {
    Long getId(); //etc...
    Set<Assignment> getAssignments();
    void setAssignments(Set<Assignment> assignments);
public interface Task {
    Long getId(); //etc...
    Set<Assignment> getAssignments();
    void setAssignments(Set<Assignment> assignments);
public interface Assignment {
    Long getId(); //etc...
    Employee getEmployee();
    void setEmployee(Employee employee);
    Task getTask();
    void setTask(Task task);
}This assumes you want to navigate in all directions: from an employee to their assignments, from a task to its assignments and from an assignment to it employee and task.

[ADF] Adding/deleting entries in a many-to-many relationship

I am using JDeveloper 10.1.3 and the ADF BC / ADF Model / ADF Faces / JSF technology stack.
For this question, I am using the SRDemo application as an example, specifically the many-to-many relationship between USERS and PRODUCTS (the Staff Expertise relationship), outlined in red in this schema diagram: Image Link
Users may have any number of product expertise areas and many users may have the same product expertise area. For the purposes of this example I have added two reference fields from the PRODUCT table into the ExpertiseAreas VO (Name and Description), outlined in red in this data control palette section: Image Link
I have created a page which shows the details of a user (1), along with a table showing the expertise areas the user has (3), and a table of all the products available (2), numbered on this design page: Image Link and corresponding to the numbered data controls on this data control palette section: Image Link, where 1 is rendered as an ADF Read-only Form, 2 is an ADF Read-only Table with a tableSelectMany element in the selection facet, and 3 is also an ADF Read-only Table.
What I am trying to do is have the tableSelectMany element reflect which of the products are linked to the current user in the expertise areas relationship (by having the checkbox for currently linked products checked), and when you check or uncheck a product's checkbox, it should add or remove the row in the EXPERTISE_AREAS intersection table, respectively (asume for this example that there are default values for Expertise Level and Notes).
So far I have been following the process used in section 19.8 of the ADF Developer's Guide for Forms/4GL Developers, which describes how to set up a selectManyShuttle which implements the adding and deleting functionality. So I have a Client Interface method in the Application Module, updateSkillsForCurrentStaff (described in section 10.6.7.2), and I have a selection listener for the assignment table in the backing bean for the page, which calls the updateSkillsForCurrentStaff method:
public void selectionChanged(SelectionEvent event)
BindingContainer bc = getBindings();
DCIteratorBinding productsIB = (DCIteratorBinding)bc.get("ProductListIterator");
Set keys = getTable1().getSelectionState().getKeySet();
Iterator iter = keys.iterator();
List productIds = new Vector();
while (iter.hasNext())
    String product = ((Key)iter.next()).toStringFormat(true);
    productsIB.setCurrentRowWithKey(product);
    ViewRowImpl productRow = (ViewRowImpl)productsIB.getCurrentRow();
    Number productId = (Number)productRow.getAttribute("Id");
    productIds.add(productId);
OperationBinding ob = bc.getOperationBinding("updateSkillsForCurrentStaff");
Map pm = ob.getParamsMap();
pm.put("productIds", productIds);
ob.execute();
All of this works, but I can't work out how to link the selection state of the assignment table to the expertise areas that are linked to the user. Also I think the method listing above must be a bit of a hack, but I don't know enough about this to know if there's an easier way of doing it.
Any help is appreciated.

Have a look at this example I cooked up for you.
http://radio.weblogs.com/0118231/2006/10/03.html#a739
It might not be the first way one thinks to implement something, but it illustrates a very interesting, model-centric approach to the problem you propose.
My feelings won't be hurt if you prefer a more view-centric approach, but I wanted to illustrate what was a maximally-model-centric solution (in fact, which doesn't even require a backing bean!) If you like a more view-centric approach, I can help you figure out what's wrong with your key-handling above. For one, I would probably start by passing the Set of Key's directly to the middle tier application module method to eliminate client-side code.
Check it out and let me know what you think. Try it directly in the Business Components Tester to appreciate one of the benefits a model-centric solution can bring.

How to design many to many relationship in the fact and dimension

There is a problem in my project what is the subject.And i wanna know how to implement in owb.I use the warehouse builder 10. Thanks.

You may design and load whatever db model you want to.
But If you set a unique key, you may find some integrity issues. I wouldn't do a many to many relationship between facts and dimensions. This could cause you lots of headaches when users start to submit queries using this tables. You'll probably face performance issues.
Regards,
Marcos

Many to Many relationship betwee dimension and fact tanle

Hello Gurus,
I have a little question about many to many realtionship between fact and dimension table. The situation is as follows.
Consider there is a fact table F1 and two dimension tables D1 and D2. D1 is joined to F1 with 1 to many relationship. D1 is joined to D2 with again one to many relationship ( Note: D1:D2 = 1:N and D1:F1 = 1:N). I am able to model this by merging D1 and D2 into one dimension table in BMM layer by adding them as logical table sources and creating logical table source join. I have built simple reports and the data returnned is fine. However, I would just like to know what could be the drawbacks of such a model.
We have many other dimesions joined to the fact table and users have access to the answers that means they would could what ever report they feel like. Hence, would just like to know in what cases this model could break which means reports would give wrong data because of a many to many relationship between one of the fact and dimension table.
Thanks in advance.

Hello Copter,
Even I had modeled it by reading this link before. In the situation explained by me dimension D1 is doing the job of table Rules ( as explained in link). The model is fine.
However, my point is to undersatnd in which scenerios this model will break. As already explained, the fact table is joined to various other dimensions, there could be situations in which users select columns from various dimensions and facts randomly.
Hence, which are the scenerios where I might get erroneous counts of meassures. Further, if someone feels this model is correct and would not break in any scenerio then please reply.

Many to many relationships between Fact and Dimension

Hi All,
I have to solve two kind of many to many relationships between Fact and Dimension.
1. Many to Many relationship between Fact and Dimension, using a bridge table, with FKs in fact and dimension to bridge tables PK.
2. Many to Many relationship between Fact and Dimension, using a bridge table, and an intersection table, with FK in fact to bridge table, and 2 FKs in intersection table to Dimension and to bridge table.
I need help on implementing (how the mapping has to look like) them in OWB 9.2.0.2.8.
Thanks,
Aurelian Cojocaru

Aurelian,
Unfortunately, you cannot implement this in the dimensional model. You would have to use relational tables and relationships between those in order to implement your scenario.
Thanks,
Mark.

SSAS - Many to Many Relationship Grain Filters Out Data (Many to One)

I have a simple Many to One example: One Fact Table record has many Dimensional Items. The Example I'm using is One FactEvent record can have multiple EventMembers. These members are always unique so the relationship is really many to one (vs.
many to many). The grain of the Fact is one row for every event. Not all events have members, but I have stubbed those with -1
I tried using a Referenced dimensional relationship, but it threw my total counts off. I decided to make it more complicated by using a
Many to Many relationship, but I had issues once I started slicing the data.
The following are my two very simple tables:
FactEvents:
EventMemberID MemberKey EventMemberKey MemberName MemberGender
1             1         -1             None       N
2             2         E2             Tyler      M
3             3         E2             John       M
4             4         E2             Sue        F
5             5         E5             Tim        M
6             6         E5             Jane       F
7             7         E12            Ashley     F
8             8         E12            Jessica    F
9             9         E12            Kristy     F
10            10        E17            Mike       M
11            11        E17            Josh       M
12            12        E18            Warren     M
13            13        E18            Eric       M
Here is the bridge Table:
EventID EventBK EventName         EventMemberKey EventCount
1       E1      Hockey Game       -1             1
2       E2      Soccer Game       E2             1
3       E3      Baseball Game     -1             1
4       E4      Concert           -1             1
5       E5      Food Festival     E5             1
6       E6      Movie Night       -1             1
7       E7      Data Group Event -1             1
8       E8      City Tour         -1             1
9       E9      Ski Trip          -1             1
10      E10     Camping Trip      -1             1
11      E11     Hiking Trip       -1             1
12      E12     Community Cleanup E12            1
13      E13     Block Party       -1             1
14      E14     Toastmasters      -1             1
15      E15     Train Spotting    -1             1
16      E16     Plane Spotting    -1             1
17      E17     Fishing Trip      E17            1
18      E18     Hunting Trip      E18            1
19      E19     Street Hockey     -1             1
20      E20     Bonspiel          -1             1
You can see many events have no members and some events have multiple members. There is not separate members Dim, just the bridge table. I tried to build view that would work as bridge tables, but it started to feel like overkill.
Here is the SSAS structure:
Cube:
I tried creating a bridge Dim and Measure Group that can be used to join FactEvents with DimMemberEvent:
When I query the database tables directly, I can get the structure I'm looking for:
Gender Count
F            5
M           7
N           15
This represents that although there are 20 events, there were 5 Female and 7 Male participants and 15 events with No participants. When looking at the cube in excel I get:
Gender Count
F            3
M           4
N           15
Grand Total 20
The grand total is correct, however, it looks like it is grouping the events, so if there are multiple Female members at a particular event, they get rolled up. You can see this better if I pull in member name:
It includes all the names with count 1 ie. 5 Females with count 1, but the gender subtotal is 3 (as it is grouping the gender dimension)
The detail member counts are good, but the rolled up M and F counts are stripping out duplicates. Is there a way to model this in SSAS to preserve the detail member counts when the member dimension is used? Is a many to many the best solution?
This is all using SQL Server 2012 Multi-Dimensional Model. Thanks.

Ok, for starters, if it's a one to many relationship, don't set it up as a many to many! Avoid many to many relationships and really anything other than "regular" relationships.
Second, the tables you pasted the data for aren't the tables you are describing them as, based on the dsv screenshot you included. If your post is confusing to the people who are wanting to help you, they will quickly move on.
It seems that you are not clear on how to construct a star schema. I will lay one out for you and hopefully this can help you on your journey.
fact_member_event:
event_id
member_id
member_event_count
dim_member:
member_id
member_key
member_name
member_gender
dim_event:
event_id
event_name
fact_event:
event_id
event_count
Or alternately, you could drop the fact_event fact table and have a calculated member that uses dimEvent.event.event.allmembers.count. It's a little bit of a weird situation that I would want to play with, but I would start with the above.
Also if you post back and show query results, you should make it clear what columns you are displaying. I see "count" in your query above, but nowhere in the star schema do I see "member count"
as a field.. I guess that's event count?
Hope this helps,
Ken

Many to Many relationship - Bridge Table

This post may be more appropriate for a data modeling discussion group, but thought I would post here because it will ultimately be modeled/used in OBIEE.
Can someone help me understand what the point/use is for a Bridge table when managing a many to many relationship between a fact table and a dimension? I have read a hundred different ways to handle this situation with the brige table method being the overwhelming approved approach .. but I don't see what a bridge table specifically buys you (Im sure Im missing something though).
For example .. If I have:
EVENT_FACT
EFkey
CRDimKey
Famount
CUSTOMER_ROLE_DIM
CRDimKey
Customer Name
Role
So a customer can hold multiple roles and therefore 1 event fact record could link to multiple CUSTOMER ROLE records and 1 customer role record will most likely link to multiple EVENT_FACT records.
As I understand the bridge approach would put a bridge table CUSTOMER_ROLE_EVENT_BRIDGE in place like follows:
CUSTOMER_ROLE_EVENT_BRIDGE
EFkey
CRDimkey
WeightFactor
With this approach you now have the following setup:
EVENT_FACT one-to-many CUSTOMER_ROLE_EVENT_BRIDGE
CUSTOMER_ROLE_DIM many-to-many CUSTOMER_ROLE_EVENT_BRIDGE
Doesn't a many to many relationship still exist from the dimension to the bridge table? Since all we did was join the dimension to the fact table to create the bridge table I dont see how the many to many from dimension to bridge doesnt exist?
It seems somewhat inneficient to join the dimension to the bridge ahead of time to create this table and place the weight factor on it. Why not just compute the weight factor of the dimension and place that as a field on the dimension itself and use it when joined to the fact table?
Thanks for the help and insight!!
k
Edited by: user_K on May 19, 2010 4:34 PM

I'm developing a CS degree project with 2 professors, Matteo Golfarelli and Stefano Rizzi, who have developed the Dimensional Fact Model for data warehouses and wrote many books about it.
They followed the Kimball theory about N:N and used its bridge table concept, so when I said them that in OBIEE there is this definition they were very happy.
But they stopped this happiness when I said that bridge tables only connect fact tables to dimension tables, and to create N:N between levels at higher aggregation we should use logical joins as you said in your blog. I need to extract metadata concepts from UDML exportation language, and about N:N I can do it only with bridge table analysis, I can't extract and identify a N:N level relationship from a multiple join schema as in your blog... this is the limit of your solution for our project, only this!
PS: sorry for my english, I'm italian!
thanks for the replies!

Many to many relationship problem

Hi folks!
I am having the following problem when mapping many-to-many relationships: "More than one writable many-to-many mapping cannot use the same relation table".
This is what I am doing: I have a class Person and a class Meeting. One Person has many meetings and one Meeting has many participants (person).
I did the M-to-M relationship for the class Person and it worked fine in the workbench. But when I tried to do it in the Meeting class the workbench complained with that error.
I believe it might be a problem with the source and target references but I couldn't figure out how to solve it.
If I check in the intermediate table there are only 2 references created.
Can anyone help?

Hello,
Firstly, think about object model consistency (without TopLink or other persistence layer at all): should you be changing one side (eg Person), adding a meeting, without changing the other side? Is that object model self-consistent? It doesn't appear so to me- I can navigate from meeting to person and not get the same results as navigating from person to meeting. All this is irrespective of the persistence layer.
TopLink, first and foremost, expects that your object model is self-consistent. If it is, then you will find that the problem you indicate is no longer a problem- if i update a person with a new meeting, i change the meeting to person relationship as well. This means that although one direction is read-only to TopLink, the other is not- so the data will be written.
I hope this helps,
Christian

Many-to-many relationship performance problem

Hi:
I have model that uses a bridge table to solve a many-to-many relationship. Here it is:
dimension 1 -< fact table >-dimension 2-< bridge table >-additional data table
Now, when I drive from the additional data table with a specific value and join to the bridge table and dimension 2, the performance is fine. But, as soon as I add the fact table to the query, the query never returns. I'm in a development environment, so my fact table has 220K records, and the bridge table has 200K records. The dimension 2 and additional data tables have hundreds of records. In other words, it's not much data. I have indexes and referential constraints on all relevant columns.
Can anyone suggest what is happening to cause such a performance hit when I add the fact table to the query?
Thanks for any suggestions!

sybrand_b wrote:
The way you write it yes, but there is one minor detail.
You can have a 0,1 or many relationship: one employee has zero, one or many phone numbers
but you can not have the opposite, as it doesn't make sense.
0, 1 or many phone numbers belong to 1 employee.
It is customary to use 0,1 or m when the relationship is optional.
Sybrand Bakker
Senior Oracle DBAIs this correct now ?
one to many : one employee has 0,1 or multiple phone numbers
many to one : 1 or multiple phone numbers to one employee

Many to many relationship issue

Guys,
How do we deal with the situation where we have many to many relationship between 2 different characteristics?
Thanks,
RG

Hi,
I assume you are talking about data modeling.
When you are required to decide how to model two Char with many to many relations
1. If you keep them in Same Dimension table the size of the dimension table will be more.
lets say 100 Customers & 100 Materials
Now if you keep them in same dimension..
lets say C1 will have combination of M1 till M100.similarly for other customers
So Total rows in dimension table will be 100x 100 = 10000!!!
It will again be of comparable size to fact table and not recommended.
2.You always try to define them in different dimensions
Now ,You try keeping them in diffrent dimension..in this case Customer dimension will have only 100 rows & Mateial dimension will have only 100 Rows.very small when compared to fact table size.
Hope this helps
Sriman

Many to Many relationship in a Dimension.

Hi all,
To improve the infocube performance , we should not keep the characteristis which is have MANY TO MANY relationship in a one dimension. My question is how to find out which characteristics is having many-many relationship.And which characteristics is having 1 to Many relationship.
Regards,
Asim

Hi Asim,
There are some very obvious ones.E.g product and product group. This is obviously 1-n relationship.But there are also the ones which you can not see easily.For those ones, you can check the data in datasource.Then you can see that these characteristics have 1-1, 1-n or n-m relationship. I don't know any easy way to do so except checking PSA manually.
In fact, if we consider that you are the BW consultant who is modelling, then you must know the meanings and relationships of characteristics.So usually you won't hesitate much while creating the dimensions as you know about the characteristics.You can also ask the users and other R3 consultants when you can not guess the result.
Here is a useful thread for the logic explained by examples:
Regards,
Güneş BÜYÜKTANIR

Modeling a many-to-many relationship in a dimension

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