Modeling a many-to-many relationship attribute

Hi, I have these dimension tables:
STORE (key, name, city, region, state)
PRODUCT (key, name, type, category)
I also have a table TAX (state, category, amount), without any foreign key constraint because STORE.state and PRODUCT.category aren't primary keys.
How can I model it using AWM? I tried snowflaking in STORE but I can't tell to AWM that TAX.amount depends either on STORE.state and PRODUCT.category...

Thanks Shankar, my tax value is a rate, so I aggregate using MAX operator.
I tried you derivated measure expression as follows:
Cube2.TaxRate(NEGOZIO_FORUM NEGOZIO_FORUM_familyrel(NEGOZIO_FORUM_levellist 'STATO') PRODOTTO_FORUM PRODOTTO_FORUM_familyrel(PRODOTTO_FORUM_levellist 'CATEGORIA'))
note that NEGOZIO_FORUM is my store dimension and PRODOTTO_FORUM my product dimension
this is the error I get:
Encountered "(" at line 1, column 14.
Was expecting one of:
<EOF>
"||" ...
"+" ...
"AT" ...
"DAY" ...
"YEAR" ...
"WHERE" ...
"=" ...
<NE> ...
"<" ...
"<=" ...
">" ...
">=" ...
"NOT" ...
"BETWEEN" ...
"LIKE" ...
"LIKEC" ...
"LIKE2" ...
"LIKE4" ...
"IN" ...
"IS" ...
at oracle.olapi.syntax.SyntaxObject.throwParseException(Unknown Source)
at oracle.olapi.syntax.SyntaxObject.fromSyntax(Unknown Source)
at oracle.olapi.syntax.SyntaxObject.fromSyntax(Unknown Source)
at oracle.olapi.syntax.SyntaxObject.fromSyntax(Unknown Source)
at oracle.olap.awm.calcxml.CalcXMLPlugin.getExpression(Unknown Source)
at oracle.olap.awm.dataobject.dialog.olapi.derivedmeasure.UDerivedMeasureGeneralPanel.setCalc(Unknown Source)
at oracle.olap.awm.dataobject.dialog.olapi.derivedmeasure.UDerivedMeasureGeneralPanel.populateDataObject(Unknown Source)
at oracle.olap.awm.dataobject.dialog.PropertyViewer.populateDataObject(Unknown Source)
at oracle.olap.awm.dataobject.dialog.PropertyViewer.doApplyAction(Unknown Source)
at oracle.olap.awm.dataobject.dialog.PropertyViewer.access$200(Unknown Source)
at oracle.olap.awm.dataobject.dialog.PropertyViewer$1ApplyThread.run(Unknown Source)
seems a syntax error... excuse me but I don't know this OLAP expression language very well...
thanks again!
Edited by: battle84 on 23-set-2009 9.50

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.

Need example of adding attributes for many-to-many relationship

Hi,
Looking for examples of mappings and update code for many-to-many relationships with attributes.
There is a doc in Metalink:206971.1 that says that it can be done but no examples are shown.
Would realllly appreciate any help you can provide.
Cheers,
Nim

Extended Many to Many Question
Really there isn't any code to show. The recommendation is to create a class to represent the relationship. See link above for more details on the issue.
- Don

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

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 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.

JPA one to many relationship and serialization

Hi,
I modeled a one to may relationship like this:
Parent Class WFData:
@OneToMany(mappedBy = "wfData", targetEntity = Positionen.class)
private Set<Positionen> positionen;
Child Class Positionen
@ManyToOne
@JoinColumn(name = "WF_REF_ID", referencedColumnName = "ID")
private WFData wfData;
Now I want to create an EJB session bean with a method which returns an object of type WFData (parent) published as web service . When I try to deploy the web service I get the following error message: Unable to generate serialization framework for web service
Does anyone know how to serialize a one-to-many relationship so I can use these objects in a web service?
Best regards,
Kevin

I found the solution to get serialization correctly working and enable the service to be used in Visual Composer.
You need to add the tag @XmlTransient to the getter method of the attribute in the child class that references the parent.
@XmlTransient
public WFData getWfData() {
return wfData;

Problem with 1-to-many relationship between entity beans

Hi All!
I have two tables TMP_GROUP and TMP_EMPLOYEE with following fields:
TMP_GROUP: ID, CAPTION, COMMENT, STATUS.
TMP_EMPLOYEE: ID, LOGIN, GROUP_ID.
For this tables i create two entity beans GROUP and EMPLOYEE respectively.
The relationship looks like this
descriptor ejb.xml:
<ejb-relation>
            <description>description</description>
            <ejb-relation-name>employeesOfGroup</ejb-relation-name>
            <ejb-relationship-role>
                <ejb-relationship-role-name>com.mypackage.GroupBean</ejb-relationship-role-name>
                <multiplicity>One</multiplicity>
                <relationship-role-source>
                    <ejb-name>GroupBean</ejb-name>
                </relationship-role-source>
                <cmr-field>
                    <cmr-field-name>employees</cmr-field-name>
                    <cmr-field-type>java.util.Collection</cmr-field-type>
                </cmr-field>
            </ejb-relationship-role>
            <ejb-relationship-role>
                <ejb-relationship-role-name>com.mypackage.EmployeeBean</ejb-relationship-role-name>
                <multiplicity>Many</multiplicity>
                <relationship-role-source>
                    <ejb-name>EmployeeBean</ejb-name>
                </relationship-role-source>
            </ejb-relationship-role>
        </ejb-relation>
descriptor persistent.xml:
<table-relation>
               <table-relationship-role
                    key-type="PrimaryKey">
                    <ejb-name>GroupBean</ejb-name>
                    <cmr-field>employees</cmr-field>
               </table-relationship-role>
               <table-relationship-role
                    key-type="NoKey">
                    <ejb-name>EmployeeBean</ejb-name>
                    <fk-column>
                         <column-name>GROUP_ID</column-name>
                         <pk-field-name>ejb_pk</pk-field-name>
                    </fk-column>
               </table-relationship-role>
          </table-relation>
Now i implement business method:
public Long addEmployee(String login, long groupId) {
          Long result;
          try {
               EmployeeLocal employee = employeeHome.create(login);
               GroupLocal group =
                    groupHome.findByPrimaryKey(new Long(groupId));
               Collection employees = group.getEmployees();
               employees.add(employee);
               result = (Long) employee.getPrimaryKey();
          } catch (CreateException ex) {
               result = new Long(0);
          } catch (FinderException ex) {
               result = new Long(0);
          return result;
When i call this method from web service, the following exception is raised:
com.sap.engine.services.ejb.exceptions.BaseTransactionRolledbackLocalException: Exception in method com.mypackage.GroupLocalHomeImpl0.findByPrimaryKey(java.lang.Object).
P.S.
1) I have transaction attribute set to "Required" for all methods of all beans
2) I have unique index for each table:
TMP_GROUP_I1: CAPTION
TMP_EMPLOYEE_I1: LOGIN (however i think GROUP_ID must be added here too)
3) I tried many:many relationship with this tables and it works fine
4) I try another implementation of addEmployee method with
EmployeeLocal employee = employeeHome.create(login, groupId);
without using GroupLocal cmr-field and GroupLocalHome findByPrimaryKey method, the result is same error.
Can somebody help me with this problem?
Thanks in advance.
Best regards, Abramov Andrey.

gimbal2 wrote:
1: The @JoinColumn on the listOfDepartments collection in Company is wrong. It should be something like this for a bidirectional relationship:
@OneToMany(mappedBy="company") // company is the matching property name in Department
private List <Department> listOfDepartment = new ArrayList<Department>();Note that I removed the fetch configuration; onetomany is fetched lazy by design. Saves some clutter eh.
2: use a Set in stead of a List (hibernate doesn't like lists much in entities and will break when you create slightly more complex entity relations)
3: don't just slap cascades on collections, especially of type ALL. Do it with care. In the many years I've been using JPA I've only had to cascade deletes in very specific situations, maybe once or twice. I never needed any of the other cascade types, they just invite sloppy code if you ask me. When working with persistence you should apply a little precision.I made all changes as you mentioned but still compID in department table shows null value...

Problem with 1:many relationship between entity beans.

Hi All!
I have two tables TMP_GROUP and TMP_EMPLOYEE with following fields:
TMP_GROUP: ID, CAPTION, COMMENT, STATUS.
TMP_EMPLOYEE: ID, LOGIN, GROUP_ID.
For this tables i create two entity beans GROUP and EMPLOYEE respectively.
The relationship looks like this
descriptor ejb.xml:
<ejb-relation>
            <description>description</description>
            <ejb-relation-name>employeesOfGroup</ejb-relation-name>
            <ejb-relationship-role>
                <ejb-relationship-role-name>com.mypackage.GroupBean</ejb-relationship-role-name>
                <multiplicity>One</multiplicity>
                <relationship-role-source>
                    <ejb-name>GroupBean</ejb-name>
                </relationship-role-source>
                <cmr-field>
                    <cmr-field-name>employees</cmr-field-name>
                    <cmr-field-type>java.util.Collection</cmr-field-type>
                </cmr-field>
            </ejb-relationship-role>
            <ejb-relationship-role>
                <ejb-relationship-role-name>com.mypackage.EmployeeBean</ejb-relationship-role-name>
                <multiplicity>Many</multiplicity>
                <relationship-role-source>
                    <ejb-name>EmployeeBean</ejb-name>
                </relationship-role-source>
            </ejb-relationship-role>
        </ejb-relation>
descriptor persistent.xml:
<table-relation>
               <table-relationship-role
                    key-type="PrimaryKey">
                    <ejb-name>GroupBean</ejb-name>
                    <cmr-field>employees</cmr-field>
               </table-relationship-role>
               <table-relationship-role
                    key-type="NoKey">
                    <ejb-name>EmployeeBean</ejb-name>
                    <fk-column>
                         <column-name>GROUP_ID</column-name>
                         <pk-field-name>ejb_pk</pk-field-name>
                    </fk-column>
               </table-relationship-role>
          </table-relation>
Now i implement business method:
public Long addEmployee(String login, long groupId) {
          Long result;
          try {
               EmployeeLocal employee = employeeHome.create(login);
               GroupLocal group =
                    groupHome.findByPrimaryKey(new Long(groupId));
               Collection employees = group.getEmployees();
               employees.add(employee);
               result = (Long) employee.getPrimaryKey();
          } catch (CreateException ex) {
               result = new Long(0);
          } catch (FinderException ex) {
               result = new Long(0);
          return result;
When i call this method from web service, the following exception is raised:
com.sap.engine.services.ejb.exceptions.BaseTransactionRolledbackLocalException: Exception in method com.mypackage.GroupLocalHomeImpl0.findByPrimaryKey(java.lang.Object).
P.S.
1) I have transaction attribute set to "Required" for all methods of all beans
2) I have unique index for each table:
TMP_GROUP_I1: CAPTION
TMP_EMPLOYEE_I1: LOGIN (however i think GROUP_ID must be added here too)
3) I tried many:many relationship with this tables and it works fine
4) I try another implementation of addEmployee method with
EmployeeLocal employee = employeeHome.create(login, groupId);
without using GroupLocal cmr-field and GroupLocalHome findByPrimaryKey method, the result is same error.
Can somebody help me with this problem?
Thanks in advance.
Best regards, Abramov Andrey.

I have posted excerpts from my orion-ejb-jar.xml file in this posting: Problem mapping a 1:M relationship between two entity EJBs w/ a compound PK
Sorry for the duplicate postings, but I was getting errors on the submission.
April

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

How to insert data in a one-to-many relationship

How do you insert data into the client, my model entity beans have a one-to-many relationship.
PARENT ENTITY BEAN
PARENT-ID
PARENT-NAME
The ejbCreate(Integer parentID,String name)
CHILD ENTITY BEAN
CHILD-ID
CHILD-NAME
PARENT-ID(foreign key of PARENTID).
ejbCreate(Integer parentID,String name,String foreignparentID)
In a jsp page i collect the parent details and 3 corresponding chld details in a text box.
Can you please tell me how do i proceed from here...
ie. how to i insert data into the entity beans..
Do i pass the child as a collection, and within parents ejbCreate() method do i lookup for the childs home interface and insert one -by -one from the collection.
1. Considering the above example, can some one pls tell how the ejbCreate() mehod signatures, for the parent and child entity beans should be.
2. Pls also show some sample client code as to how to make an insertion.
3. In case you are passing a collection of child data, then in what format does one have to insert into a collection and also how does the container know how to insert the values in the child table , bcoz we are passing as a collection.
4.In case collections cannot be inserted do we need to iterate into the collection in parent's ejbCreate() method, and manually insert into the database of the childtable, thereby creating child entity beans.
Thanks for your time and support...
regards
kartik

Hi,
3. In this case of course child's ejbCreate(and postCreate) looks like
ejbCreate(Integer childID,String name,ParentLocal parent) {
setId(Id);
setName(name);
ejbPostCreate(Integer childID,String name,ParentLocal parent) {
setParent(parent);
Here you don't need IDs, but it happens only using Locals, not Remotes, if I'm not wrong. Container does it itself.
1. Of course, if you have parent.getChildren() and parent.setChildren() then you don't need any loops, but it should be done anyway in postCreate, because in ejbCreate there no parent exists yet.
Once more 3: example - I'm using JBoss 3.2.5 as EJB container. It has tomcat inside and EJB and JSP+Struts use the same jvm. It means for me that I don't need to use remote interfaces, just locals. And in this case I can implement ejb-relations. So, a have the abstract method parent.getChildren() which returns Collection of ChildLocal - s and method parent.setChildren(Collection childrenLocals) which creates/modifies children by itself.
I have not used remotes for a long time, but as I remember it was not possible to implement ejb-relations using remotes.
regards,
Gio

Struggling with a one to many relationship in a sub-report

Post Author: Scott_tansley
CA Forum: General
I have a database schema as per below: tblENQUIRY tblDatasheets tblReportParasIRSID (PK) 1 --> & IRSID (FK) UID (PK)Attribute1 SHEETID (PK) 1 > & SHEETID (FK)Attribute2 Attribute1 LIST_ORDER tblStandardParasAttribute3 Attribute2 PARA_CODE (FK) & < 1 CODE (PK)etc... Attribute3 TEXT etc...
The PROBLEM I am a Crystal Reports Newbie, and having to work through things bit by bitu2026 I've managed to achieve quite a lot, but I'm totally stuck with this and would appreciate some help. I need to create a report (essentially a letter and some datasheets) around a one-to-many relationship, which I have managed to compile using a main report (for the one [tblENQUIRY]) and sub report (for the many [tblDatasheets]). Essentially I need a covering letter, then the u2018manyu2019 datasheets, and then a number of other pages (which are largely static text). I have created a main report which includes the covering letter, holds a subreport for the datasheets, and then contains the text for the additional pages. This all works fine, and I get the correct number of datasheets for each main report. My problem stems from the use of this sub report. This sub-report needs to hold some attribute values for each datasheet, which is fine. However, on each datasheet page I need to have some paragraphs, which are held in another one to many relationship. Each datasheet may have up to six paragraphs held as a code in tblReportParas, with a relationship to the text as held in tblStandardParas. My original thought would have been to embed another sub report, containing the values from tblStandardParas!TEXT, into the first sub report. However, I have found that it is not possible to have a sub-report inside another sub-report. I had seperated the first sub-report out from the main report, and then embedded another sub-report into it. This worked fine until I tried to stitch the sub-report back into the main report (at which point the sub-sub-report dissapeared from view). I have therefore reworked my sub-report a little, and the attribution is now stored in a pageheader, with the tblStandardParas!TEXT in a detail section below it. This almost works! The only problem is that there is no relationship between the pageheader and detail sections. To clarify, I would expect to have one datasheet, with the attribution at the top, and then the six paras below. Then, the same on the next page (assuming there is a second datasheet) for that report. Instead, I get the correct attribution, but the detail section actually gives every paragraph in the database, no matter which datasheet/or report it related to! I therefore need to limit the detail section to only show those paragraphs where the SHEETID in tblReportParas is the same as the tblDatasheets SHEETID. Any offers of advice would be appreciated.

Post Author: Scott_tansley
CA Forum: General
I managed to resolve this myself in the end. I moves the tblEnquiry data into report header/footer sections, this allowed me to add the tblDatasheets information into the details section, which gave me multiple pages - and then finally, the Paragraphs were added through the use of a sub report.
There's probably an even better way, but for now it works, it's quick - and so I'm going to go with it!
Thanks for your interest.

Defining a many-to-many relationship with CMP EJBs : does it work for you

Curious to know whether someone has been able to set up a many to many relationship between two entity beans.
I have been struggling with this for days now and I can't get it to work.
In my test project I have two entity beans, resp. Consultant and Solution.
Consultant has a cmr field called 'solutions', which is a collection object from the opposite side (Solution).
This is the source of the ejb-jar.xml file
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE ejb-jar PUBLIC "-//Sun Microsystems, Inc.//DTD Enterprise JavaBeans 2.0//EN" "http://java.sun.com/dtd/ejb-jar_2_0.dtd">
<ejb-jar>
     <description>EJB JAR description</description>
     <display-name>EJB JAR</display-name>
     <enterprise-beans>
          <session>
               <ejb-name>ProfilerBean</ejb-name>
               <home>com.atosorigin.tcc.testing.ejbses.profiling.ProfilerHome</home>
               <remote>com.atosorigin.tcc.testing.ejbses.profiling.Profiler</remote>
               <local-home>com.atosorigin.tcc.testing.ejbses.profiling.ProfilerLocalHome</local-home>
               <local>com.atosorigin.tcc.testing.ejbses.profiling.ProfilerLocal</local>
               <ejb-class>com.atosorigin.tcc.testing.ejbses.profiling.ProfilerBean</ejb-class>
               <session-type>Stateless</session-type>
               <transaction-type>Container</transaction-type>
               <ejb-local-ref>
                    <ejb-ref-name>EJBTesting/Solution</ejb-ref-name>
                    <ejb-ref-type>Entity</ejb-ref-type>
                    <local-home>com.atosorigin.tcc.testing.ejbcmp.profiling.SolutionLocalHome</local-home>
                    <local>com.atosorigin.tcc.testing.ejbcmp.profiling.SolutionLocal</local>
                    <ejb-link>SolutionBean</ejb-link>
               </ejb-local-ref>
               <ejb-local-ref>
                    <ejb-ref-name>EJBTesting/Consultant</ejb-ref-name>
                    <ejb-ref-type>Entity</ejb-ref-type>
                    <local-home>com.atosorigin.tcc.testing.ejbcmp.profiling.ConsultantLocalHome</local-home>
                    <local>com.atosorigin.tcc.testing.ejbcmp.profiling.ConsultantLocal</local>
                    <ejb-link>ConsultantBean</ejb-link>
               </ejb-local-ref>
          </session>
          <entity>
               <ejb-name>ConsultantBean</ejb-name>
               <home>com.atosorigin.tcc.testing.ejbcmp.profiling.ConsultantHome</home>
               <remote>com.atosorigin.tcc.testing.ejbcmp.profiling.Consultant</remote>
               <local-home>com.atosorigin.tcc.testing.ejbcmp.profiling.ConsultantLocalHome</local-home>
               <local>com.atosorigin.tcc.testing.ejbcmp.profiling.ConsultantLocal</local>
               <ejb-class>com.atosorigin.tcc.testing.ejbcmp.profiling.ConsultantBean</ejb-class>
               <persistence-type>Container</persistence-type>
               <prim-key-class>java.lang.String</prim-key-class>
               <reentrant>False</reentrant>
               <cmp-version>2.x</cmp-version>
               <abstract-schema-name>Consultant</abstract-schema-name>
               <cmp-field>
                    <field-name>firstname</field-name>
               </cmp-field>
               <cmp-field>
                    <field-name>lastname</field-name>
               </cmp-field>
               <cmp-field>
                    <field-name>country</field-name>
               </cmp-field>
               <cmp-field>
                    <field-name>id</field-name>
               </cmp-field>
               <primkey-field>id</primkey-field>
               <query>
                    <query-method>
                         <method-name>findBySolution</method-name>
                         <method-params>
                              <method-param>java.lang.String</method-param>
                         </method-params>
                    </query-method>
                    <ejb-ql>SELECT Object(c) FROM Consultant AS c,
                    IN(c.solutions) s WHERE s.id = ?1 </ejb-ql>
               </query>
          </entity>
          <entity>
               <ejb-name>SolutionBean</ejb-name>
               <home>com.atosorigin.tcc.testing.ejbcmp.profiling.SolutionHome</home>
               <remote>com.atosorigin.tcc.testing.ejbcmp.profiling.Solution</remote>
               <local-home>com.atosorigin.tcc.testing.ejbcmp.profiling.SolutionLocalHome</local-home>
               <local>com.atosorigin.tcc.testing.ejbcmp.profiling.SolutionLocal</local>
               <ejb-class>com.atosorigin.tcc.testing.ejbcmp.profiling.SolutionBean</ejb-class>
               <persistence-type>Container</persistence-type>
               <prim-key-class>java.lang.String</prim-key-class>
               <reentrant>False</reentrant>
               <cmp-version>2.x</cmp-version>
               <abstract-schema-name>Solution</abstract-schema-name>
               <cmp-field>
                    <field-name>description</field-name>
               </cmp-field>
               <cmp-field>
                    <field-name>name</field-name>
               </cmp-field>
               <cmp-field>
                    <field-name>parent</field-name>
               </cmp-field>
               <cmp-field>
                    <field-name>id</field-name>
               </cmp-field>
               <primkey-field>id</primkey-field>
               <query>
                    <query-method>
                         <method-name>findChildSolutions</method-name>
                         <method-params>
                              <method-param>java.lang.String</method-param>
                         </method-params>
                    </query-method>
                    <ejb-ql>SELECT Object(s) FROM Solution AS s WHERE
                    s.parent = ?1</ejb-ql>
               </query>
               <query>
                    <query-method>
                         <method-name>findTopLevelSolutions</method-name>
                         <method-params/>
                    </query-method>
                    <ejb-ql>Select Object(s) FROM Solution AS s WHERE
                    (s.parent = 'none')</ejb-ql>
               </query>
          </entity>
     </enterprise-beans>
     <relationships>
          <ejb-relation>
               <description>A consultant may have one or more areas of expertise</description>
               <ejb-relation-name>Consultant_Solutions</ejb-relation-name>
               <ejb-relationship-role>
                    <ejb-relationship-role-name>com.atosorigin.tcc.testing.ejbcmp.profiling.ConsultantBean</ejb-relationship-role-name>
                    <multiplicity>Many</multiplicity>
                    <relationship-role-source>
                         <ejb-name>ConsultantBean</ejb-name>
                    </relationship-role-source>
                    <cmr-field>
                         <cmr-field-name>solutions</cmr-field-name>
                         <cmr-field-type>java.util.Collection</cmr-field-type>
                    </cmr-field>
               </ejb-relationship-role>
               <ejb-relationship-role>
                    <ejb-relationship-role-name>com.atosorigin.tcc.testing.ejbcmp.profiling.SolutionBean</ejb-relationship-role-name>
                    <multiplicity>Many</multiplicity>
                    <relationship-role-source>
                         <ejb-name>SolutionBean</ejb-name>
                    </relationship-role-source>
               </ejb-relationship-role>
          </ejb-relation>
     </relationships>
     <assembly-descriptor>
          <container-transaction>
               <description>container-transaction</description>
               <method>
                    <ejb-name>SolutionBean</ejb-name>
                    <method-name>*</method-name>
               </method>
               <method>
                    <ejb-name>ProfilerBean</ejb-name>
                    <method-name>*</method-name>
               </method>
               <method>
                    <ejb-name>ConsultantBean</ejb-name>
                    <method-name>*</method-name>
               </method>
               <trans-attribute>Required</trans-attribute>
          </container-transaction>
     </assembly-descriptor>
</ejb-jar>
I created a stateless session bean as a business facade for the two entity beans. I then created a webservice to test the beans.
What works :
- create a consultant
- get a consultant
- create a solution
- get a solution
(basically everything that doesn't involve the relationship field.
However, what doesn't work is the method call assignSolution:
- assign solution : this is implemented as follows
Business Method.
     public void assignSolution(String consultantID, String solutionID)
          throws ProfilingException {
          // TODO : Implement
          ConsultantLocal cons = null;
          SolutionLocal sol = null;
          try {
               cons = consHome.findByPrimaryKey(consultantID);
               sol = solHome.findByPrimaryKey(solutionID);
               Collection solutions = cons.getSolutions();
               solutions.add(sol);
               //sol.getConsultants().add(cons);
          } catch (FinderException ex) {
               ex.printStackTrace();
               throw new ProfilingException("failed to retrieve data from DB", ex);
As you can see I am trying to use the CM Relationship in this methhod. Adding the solution to a consultant should be as simple as adding a solution object to the collection retrieved with the getSolutions accessor. The Container is expected to persist the information in my MAXDB database.
However this doesn't happen.
The ORM details as defined in the persistent.xml follows :
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE persistent-ejb-map SYSTEM "persistent.dtd">
<persistent-ejb-map>
     <locking
          type="Table"/>
     <db-properties>
          <data-source-name>TCC_PORTAL_PROFILER</data-source-name>
          <database-vendor
               name="SAPDB"/>
     </db-properties>
     <entity-beans>
          <entity-bean>
               <ejb-name>ConsultantBean</ejb-name>
               <table-name>PFL_CONSULTANTS</table-name>
               <field-map
                    key-type="NoKey">
                    <field-name>firstname</field-name>
                    <column>
                         <column-name>FIRSTNAME</column-name>
                    </column>
               </field-map>
               <field-map
                    key-type="NoKey">
                    <field-name>lastname</field-name>
                    <column>
                         <column-name>LASTNAME</column-name>
                    </column>
               </field-map>
               <field-map
                    key-type="NoKey">
                    <field-name>country</field-name>
                    <column>
                         <column-name>COUNTRY</column-name>
                    </column>
               </field-map>
               <field-map
                    key-type="PrimaryKey">
                    <field-name>id</field-name>
                    <column>
                         <column-name>ID</column-name>
                    </column>
               </field-map>
               <finder-descriptor>
                    <method-name>findBySolution</method-name>
                    <method-params>
                         <method-param>java.lang.String</method-param>
                    </method-params>
                    <load-selected-objects
                         lock="read"/>
               </finder-descriptor>
          </entity-bean>
          <entity-bean>
               <ejb-name>SolutionBean</ejb-name>
               <table-name>PFL_SAPSOLUTIONS</table-name>
               <field-map
                    key-type="NoKey">
                    <field-name>description</field-name>
                    <column>
                         <column-name>DESCRIPTION</column-name>
                    </column>
               </field-map>
               <field-map
                    key-type="NoKey">
                    <field-name>name</field-name>
                    <column>
                         <column-name>NAME</column-name>
                    </column>
               </field-map>
               <field-map
                    key-type="NoKey">
                    <field-name>parent</field-name>
                    <column>
                         <column-name>PARENTID</column-name>
                    </column>
               </field-map>
               <field-map
                    key-type="PrimaryKey">
                    <field-name>id</field-name>
                    <column>
                         <column-name>ID</column-name>
                    </column>
               </field-map>
               <finder-descriptor>
                    <method-name>findChildSolutions</method-name>
                    <method-params>
                         <method-param>java.lang.String</method-param>
                    </method-params>
                    <load-selected-objects
                         lock="read"/>
               </finder-descriptor>
               <finder-descriptor>
                    <method-name>findTopLevelSolutions</method-name>
                    <method-params/>
                    <load-selected-objects
                         lock="read"/>
               </finder-descriptor>
          </entity-bean>
     </entity-beans>
     <relationships>
          <table-relation>
               <help-table>PFL_CONS_SOL_MAP</help-table>
               <table-relationship-role
                    key-type="PrimaryKey">
                    <ejb-name>ConsultantBean</ejb-name>
                    <cmr-field>solutions</cmr-field>
                    <fk-column>
                         <column-name>CONSULTANTID</column-name>
                         <pk-field-name>id</pk-field-name>
                    </fk-column>
               </table-relationship-role>
               <table-relationship-role
                    key-type="PrimaryKey">
                    <ejb-name>SolutionBean</ejb-name>
                    <fk-column>
                         <column-name>SOLUTIONID</column-name>
                         <pk-field-name>id</pk-field-name>
                    </fk-column>
               </table-relationship-role>
          </table-relation>
     </relationships>
</persistent-ejb-map>
The error in the default trace file when calling the method states, there is an "inconsistency in the number of primary keys". Details follow.
#1.5#000F1F188E5C004400000000000010480003E76C80EFD57A#1098880364327#com.sap.engine.services.ejb#com.atosorigin.tcc/EJBCMPProfilingTest#com.sap.engine.services.ejb#Guest#2####4d2b2370281411d9a40d000f1f188e5c#SAPEngine_Application_Thread[impl:3]_31##0#0#Error##Java###
[EXCEPTION]
#1#com.sap.engine.services.ejb.exceptions.BaseRemoteException: Exception in method assignSolution.
     at com.atosorigin.tcc.testing.ejbses.profiling.ProfilerObjectImpl0.assignSolution(ProfilerObjectImpl0.java:822)
     at com.atosorigin.tcc.testing.ejbses.profiling.Profiler_Stub.assignSolution(Profiler_Stub.java:533)
     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
     at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
     at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
     at java.lang.reflect.Method.invoke(Method.java:324)
     at com.sap.engine.services.ejb.session.stateless_sp5.ObjectStubProxyImpl.invoke(ObjectStubProxyImpl.java:187)
     at $Proxy73.assignSolution(Unknown Source)
     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
     at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
     at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
     at java.lang.reflect.Method.invoke(Method.java:324)
     at com.sap.engine.services.webservices.runtime.EJBImplementationContainer.invokeMethod(EJBImplementationContainer.java:126)
     at com.sap.engine.services.webservices.runtime.RuntimeProcessor.process(RuntimeProcessor.java:146)
     at com.sap.engine.services.webservices.runtime.RuntimeProcessor.process(RuntimeProcessor.java:68)
     at com.sap.engine.services.webservices.runtime.servlet.ServletDispatcherImpl.doPost(ServletDispatcherImpl.java:92)
     at SoapServlet.doPost(SoapServlet.java:51)
     at javax.servlet.http.HttpServlet.service(HttpServlet.java:760)
     at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
     at com.sap.engine.services.servlets_jsp.server.HttpHandlerImpl.runServlet(HttpHandlerImpl.java:385)
     at com.sap.engine.services.servlets_jsp.server.HttpHandlerImpl.handleRequest(HttpHandlerImpl.java:263)
     at com.sap.engine.services.httpserver.server.RequestAnalizer.startServlet(RequestAnalizer.java:339)
     at com.sap.engine.services.httpserver.server.RequestAnalizer.startServlet(RequestAnalizer.java:317)
     at com.sap.engine.services.httpserver.server.RequestAnalizer.invokeWebContainer(RequestAnalizer.java:810)
     at com.sap.engine.services.httpserver.server.RequestAnalizer.handle(RequestAnalizer.java:238)
     at com.sap.engine.services.httpserver.server.Client.handle(Client.java:92)
     at com.sap.engine.services.httpserver.server.Processor.request(Processor.java:147)
     at com.sap.engine.core.service630.context.cluster.session.ApplicationSessionMessageListener.process(ApplicationSessionMessageListener.java:37)
     at com.sap.engine.core.cluster.impl6.session.UnorderedChannel$MessageRunner.run(UnorderedChannel.java:71)
     at com.sap.engine.core.thread.impl3.ActionObject.run(ActionObject.java:37)
     at java.security.AccessController.doPrivileged(Native Method)
     at com.sap.engine.core.thread.impl3.SingleThread.execute(SingleThread.java:94)
     at com.sap.engine.core.thread.impl3.SingleThread.run(SingleThread.java:162)
Caused by: com.sap.engine.services.applocking.exception.SAPAppLockingIllegalArgumentException: Inconsistency in number of primary keys
     at com.sap.engine.services.applocking.TableLockingImpl.getArgument(TableLockingImpl.java:385)
     at com.sap.engine.services.applocking.TableLockingImpl.lock(TableLockingImpl.java:128)
     at com.sap.engine.services.applocking.TableLockingImpl.lock(TableLockingImpl.java:138)
     at com.sap.engine.services.ejb.entity.pm.lock.TableLockingSystem.write(TableLockingSystem.java:82)
     at com.sap.engine.services.ejb.entity.pm.PersistentM2M.create(PersistentM2M.java:172)
     at com.sap.engine.services.ejb.entity.pm.PersistentCacheM2M.add(PersistentCacheM2M.java:197)
     at com.sap.engine.services.ejb.entity.pm.multiple.CollectionM2M.add(CollectionM2M.java:57)
     at com.atosorigin.tcc.testing.ejbses.profiling.ProfilerBean.assignSolution(ProfilerBean.java:201)
     at com.atosorigin.tcc.testing.ejbses.profiling.ProfilerObjectImpl0.assignSolution(ProfilerObjectImpl0.java:771)
     ... 32 more
I can't figure out what the problem is with the ORM mapping defined.
On the database level I have three tables. Consultant maps to PFL_CONSULTANT, Solution to PFL_SAPSOLUTIONS. The third table PFL_CONS_SOL_MAP is the help table used for the relationship (having two fields, which are in fact foreign keys from the other two tables to express the assignment of solutions to consultants (where a consultant can have one or more solutions).
ps. : I am running Netweaver Developer Workplace (Netweaver 2004, at stack level 5)
Message was edited by: Theo Paesen

Hm, after disabling 'automatic locking' it works.

[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.

Hierarchical query with many-to-many relationship

I have read with interest the creative solutions to complex hierarchical queries posted previously; they have been instructive but have not quite addressed this scenario.
We have a hierarchy table H, with columns for ID, name, parentID, and other attributes.
Within this table are a number of independent hierarchies, each existing for a different purpose.
We have a master list of hierarchies in table T which describes the purpose of each hierarchy, provides some default attributes which the nodes can inherit, and stores a unique id for each hierarchy and a pointer to the root node of the corresponding hierarchy in table H.
We have a master list of items M, with identically named columns to those in H, along with many other attributes.
The members of table M ALL belong to EACH of the Hierarchies. So we have a link table I to define the intersection of H and M.
So the leaf nodes of H are really containers for the list of elements from M which may be attached to them.
The universe of M is very volatile, with new members being added, old ones deleted, and existing ones being reclassified frequently from node to node within each hierarchy. Since the hierarchies have to be built to handle every possible scenario, so that the members of M can always find a suitable node to reside in, quite often, in fact more often than not, the majority of leaf nodes for each hierarchy are empty at any given moment.
Therefore, although we always know the root sector of a given hierarchy and can traverse downwards from there, if we worked our way up from the intersection table, we could eliminate up to 70% of the nodes of any given hierarchy from further consideration, as they don't need to be (in fact, must not be) included in reports.
As implied by the above, rows in M are structurally similar (in terms of columns, but not in any real world sense) and are a superset of rows in H. But combining them into the one table doesn't seem to help the reporting process due to the many-to-many relationship which prevents the ID/parentID relationship from being carried through to this level.
There are a number of other considerations of which the most pertinent is that the people using this database generally have an interest in only a subset of the master list of items in M. This relationship is also dynamic but important enough and rigid enough that another link table P exists to combine the Users in table U with the subset of M in which they are interested. (The users are also grouped into hierarchies of a totally different nature, but this aspect is secondary for now.)
The reporting is reasonably straightforward for any single combination of User and Hierarchy; they want to see all the items they are interested in, listed in hierarchical sequence, totalled on change of level with the individual items M listed beneath the nodes of H. This is unfortunately required in real time, so retrieval performance is paramount.
Some statistics might help to determine the optimum approach:
The largest hierarchy has 10,000 nodes. The smallest about 100.
The largest would have 70% or more of its nodes unused at any point in time, and even the smallest would have 25% unused.
The hierarchies tend to be broad rather than deep, the maximum number of levels being about 5; but the larger ones should be twice as deep as this if performance was not compromised.
There are dozens of hierarchies, but it may be possible to sharply reduce this number by exploiting the Order Siblings By clause.
The number of rows in M varies between 500,000 and 50,000; depending upon how long historical data is retained on-line (and performance permitting, it would be retained indefinitely).
The number of users varies between 1000 and 2000 but the range of M in which they are interested varies greatly; from as few as 100 to as many as 10,000+. So it is almost always worth beginning by eliminating the items in which they are not interested, implying once again that the hierarchy should be traversed upwards rather than down from the root.
The current system is very old and survives by a tactic of building what are essentially materialised views of the database structure for each user overnight using, ahem, non-relational technology. This is inefficient and not easily scaled (but it works) and hence this redevelopment project needs to (a) work, and (b) work better and faster.
I am happy to provide some DDL scripts if that helps explain the problem better than this narrative.
I can't help feeling that the solution lies in somehow extending the hierarchical query past the many-to-many link table so that the Master list can be merged directly into the hierarchy such that the M items become the leaf nodes rather than the design outlined above - but I don't know how to do that. But I am sure everyone reading this does! :)
All advice appreciated. Database version is not an issue; we are currently using version 10XE for experimentation, but production usage could be on 11 if that contains helpful features.
Thank you
CS

Hi,
ChrisS. wrote:
I am happy to provide some DDL scripts if that helps explain the problem better than this narrative.Yes, please do.
The problem seems interesting, I'm sure many people here (including myself) are willing to help you in this matter.
So yes, post DDL for the tables, as well as INSERTs to populate them with representative data. Please also include the output you require along with detailed explanations about the logic to get it.
Don't forget to put lines of code between {code} tags in order to preserve formatting and readability, like this :
SELECT sysdate FROM dual;Thanks.

Modeling a many-to-many relationship attribute

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