Confused with one to many relationship

Hi Masters ,
Reading about one to many : i came across this
Each row in Table A can have many (zero or more)
matching rows in Table B but each row in Table B
has only one matching row in Table A.
A ZipCode can have many Students but each Student has only
one ZipCode
Theoritically this would be fine but can anyone please make tables for the above so i want to see it pratical work.

zip
(zipcode varchar2(6)
, low_street_number varchar2(10)
, high_street_number varchar2(10)
, odd_even char(1)
, city varchar2(30)
, constraint zip_pk primary key (zipcode)
student
(studentno number(10)
, firstname varchar2(30)
, lastname varchar2(30)
, zipcode varchar2(6)
, constraint zip_fk foreign key(zipcode) references zip_pk
Sybrand Bakker
Senior Oracle DBA

Similar Messages

SSAS 2008 snowflake - dimensions with one-to-many relationship (NOT fact table) and hierarchy?

Hi, below is my data model for SSAS 2008 on snowflake schema.
Below is SQL Server DW tables:
DimStudent - StudentID [primarykey], StudentName, DateOfBirth, AddressID
DimStudentAddresses - AddressID [primarykey], StudentID [foreignkey], ddressLine1, AddressLine2, AddressType
FactEnrolment - StudentID, EnrolWeek, EnrolFees
So here FactEnrolement.StudentID is joined to DimStudent.StudentID column,
and relationship between DimStudent & DimeStudentAddresses is one to many I.e. one student can have multiple addresses like primary or secondry address.
To design snowflake schema in SSAS 2008 BIDS project :
[Question-1] how to join one-to-many dimensions (NOT fact table) Like DimStudent & DimAddresses?
[Question-2] At the end I want to have a single dimension only I.e. Student which should have both DimStudent & DimStudentAddresses tables attributes init. So I can create hierarchy from these two table into a single dimension? How
to do this?
Please reply with feedback particular to my above scenario as I refereed other MSDN forums but nothing solid I found.
Any STEP-BY-STEP guideline please. Many thanks.

Hello KM,
Have you solved this issue after refer to Bill's suggestion? Please let us know how things go.
If you have any feedback on our support, please click
here.
Best Regards,
Elvis Long
TechNet Community Support

About inserting with one to many relationship

db and dev 10g rel2 ,
hi all ,
using emp and dept tables of scott/tiger schema .
if i have a form , how can i insert 4 new employees in a specific dept ? what blocks should i build , and how can the user inserts into these blocks ?
thanks in advance

the user should write "20" in the deptno field once , and write the 4 new employees' data .To do this, you create a relationship between the blocks with the Dept block to be the Master and the Emp block to be the detail block. Your Form layout would look something like the following:
|---------------------------------------|
| [     ] Department Number             |
|---------------------------------------|
| Employee data...                      |
| [    ] Emp ID                         |
| [               ] First Name          |
| ...rest of the columns listed here... |
|---------------------------------------|Once you have created the relationship, Forms will handle the rest. Just run your form, select department 20 and start adding new employees.
Craig...

Formatting Issue - datatables with one to many relationship

Hi...
I am a newbie and I have designed a report in CR2008 and my datasource for the report is an XSD file. There are 2 tables Table A and B.
Table A is as follows:
AID     Name     Reference     Period          Manager
5       Name 1     Ref 1          July 2009     User Name 1
8     Name 2     Ref 2          August 2009     User Name 2
9     Name 3     Ref 3          March 2009     User Name 9
45     Name 4     Ref 4          May 2008     User Name 4
88     Name 5     Ref 5          June 2009     User Name 1
There are other coloumns too in the datatable, but that shouldnt matter.
Table B is as follows:
ID     A_ID     DateKey     DateValue          Name
1     5     Date1     2009-09-29 00:00:00.000     Start Date
2     5     Date2     2009-08-11 00:00:00.000     Fieldwork Complete
3     5     Date3     2009-08-14 00:00:00.000     Report Issued
4     5     Date4     2009-07-17 00:00:00.000     Report Finalised
5     5     Date5     2009-07-10 00:00:00.000     Close Date
6     8     Date1     2009-08-11 00:00:00.000     Start Date
7     8     Date4     2009-09-29 00:00:00.000     Report Finalised
I want the report to be in the following format:
ID     Name     Reference     Period     Manager     StartDate     Fieldwork          ReportIssue     Finalised      Closed
I have written a formula to display the date value where the date key matches for A_ID.
But when I run the report I get the result as follows:
ID     Name     Reference     Period     Manager     StartDate     Fieldwork          ReportIssue     Finalised      Closed
5     Name1     Ref1          July 2009     UName 1     29/09/2009
                                        11/08/2009                                                                                          14/08/2009                                                                                          17/07/2009                                                                                     10/07/2009

Hi
I tried what you suggested, but it hasnt worked.
In your code, you have used the date ID,
if {b.id} = 1 then
formula = {b.datevalue}
end if
but the table contains dates from several A_IDs, and I want to get the dates for the respective A_ID, So shouldnt I be matching the A_ID's first? I also dont understand how the max function helps here?
My report is already grouped by Table A, ID.
My report should be a join of the two tables, a left outer join to be exact.
Also, if my XML data contains only one record for Table A, dates still come out in a separate line. I dont quite understand where the problem is?
Thank you...

One-to-many relationships problem

Hi,
I'm having some problems with one-to-many relationships.
I've a two way relationship beetwen Person and Document.
Person has a collection of Documents (1-n).
Document has an instance for Person.
In my database schema Document has a FK for person.
The problem occurs when I'm trying to save the Person object
with a collection of Documents.
Oracle gives me the following message:
ORA-00001: unique constraint (SMS.PK_PERSON) violated
In my kodo.properties file I put:
kodo.jdbc.ForeignKeyConstraints: true
It seems that when the collection of Documents is persisted, kodo tries to
save a new Person object for each Document.
When I have just one instance of Document in my collection kodo persists
it ok, but when I have move instances I get
that problem.
Can somebody help me?
Thanks in advance,
Joan Caffee

You need to make sure each Document references the same Person object in
the JVM. JDO persists your object model as-is. Each distinct JVM
object becomes a distinct database record. You can't have multiple JVM
objects in the same PersistenceManager representing the same database
record.

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.

One-to-many relationship: problem with several tables on the one side...

Hello
I'm having problems developing a database for a content management system. Apart from details, I've got one main table, that holds the tree structure of the content ("resources") and several other tables that contain data of a particular datatype ("documents", "images", etc.). Now, there's one-to-many relationship between "resources" table and all the datatype tables - that is, in the "resources" table there's "resource_id" column, being a foreign key referenced to the "id" columns in the datatype tables.
The problem is that this design is deficient. I can't tell form the "resource_id" column from which datatype table to get the data. It seems to me that one-to-many relationship only works with two tables. If the data on the one side of the relationship is contained in several tables, problems arise.
Anybody knows a solution? I would be obliged.
Regards
Havocado

Hi;
A simple way may be create a view on referenced tables:
Connected to Oracle Database 10g Express Edition Release 10.2.0.1.0
Connected as hr
SQL>
SQL> drop table resources;
Table dropped
SQL> create table resources(id number, name varchar2(12));
Table created
SQL> insert into resources values(1,'Doc....');
1 row inserted
SQL> insert into resources values(2,'Img....');
1 row inserted
SQL> drop table documents;
Table dropped
SQL> create table documents(id number, resource_id number,type varchar2(12));
Table created
SQL> insert into documents values(1,1,'txt');
1 row inserted
SQL> drop table images;
Table dropped
SQL> create table images(id number, resource_id number,path varchar2(24));
Table created
SQL> insert into images values(1,2,'/data01/images/img01.jpg');
1 row inserted
SQL> create or replace view vw_resource_ref as
2    select id, resource_id, type, null as path from documents
3      union
4     select id, resource_id, null as type, path from images;
View created
SQL> select * from resources r inner join vw_resource_ref rv on r.id = rv.resource_id;
        ID NAME                 ID RESOURCE_ID TYPE         PATH
         1 Doc....               1           1 txt
         2 Img....               1           2              /data01/images/img01.jpg
SQL> Regards....

Need help mapping one-to-many relationship

[Sorry, inadvertently cross-posted]
Hello,
I have a one-to-many mapping question that's probably a no-brainer for the
experts of the group out there. My problem is that I can't get a collection
of Items for a given Theme to be populated and I don't know if it's a
problem in my system.jdo or in my classes (or both). For example, for Theme
10,
I want a collection of two Items, item_ids 1 and 2.
I have db tables named ITEM and THEME with the following layouts:
ITEM
|==========================================================|
| item_id(pk) | item_name | item_number | theme_id(fk) |
|==========================================================|
| 1 | This is Item1 | 1234 | 10 |
| 2 | This is Item2 | 2954 | 10 |
| 3 | This is Item3 | 2094 | 17 |
| 4 | This is Item4 | 946 | 11 |
| ... |
|==========================================================|
THEME
|=======================================|
| theme_id(pk) | theme_description |
|=======================================|
| 4 | Space |
| 10 | Town |
| 11 | Train |
| 17 | Pirate |
| ... |
|=======================================|
I have two PersistenceCapable classes that map to the above tables:
package com.lego.data;
public class Item
public int item_id;
private String item_number;
private String item_name;
private int theme_id;
public Theme theme;
public String toString()
return
item_number+":"+item_name+":"+theme.getCode()+":"+theme.getDescription();
package com.lego.data;
import java.util.*;
public class Theme
public int theme_id;
public String theme_description;
public Collection items;
public String toString()
return theme_id+":"+theme_description;
and here is my system.jdo file:
<?xml version = "1.0" encoding = "US-ASCII"?>
<jdo>
<package name="com.lego.data">
<class name="Item" identity-type="application"
objectid-class="com.lego.data.IntOId">
<extension vendor-name="kodo" key="table" value="item"/>
<extension vendor-name="kodo" key="lock-column" value="none"/>
<extension vendor-name="kodo" key="class-column" value="none"/>
<field name="item_id" primary-key="true">
<extension vendor-name="kodo" key="data-column" value="item_id"/>
</field>
<field name="item_number">
<extension vendor-name="kodo" key="data-column" value="item_number"/>
</field>
<field name="item_name">
<extension vendor-name="kodo" key="data-column" value="item_name"/>
</field>
<field name="theme_id">
<extension vendor-name="kodo" key="data-column" value="theme_id"/>
</field>
<field name="theme">
<extension vendor-name="kodo" key="theme_id-data-column"
value="theme_id"/>
</field>
</class>
<class name="Theme" identity-type="application"
objectid-class="com.lego.data.ThemeKey">
<extension vendor-name="kodo" key="table" value="theme"/>
<extension vendor-name="kodo" key="lock-column" value="none"/>
<extension vendor-name="kodo" key="class-column" value="none"/>
<field name="theme_id" primary-key="true">
<extension vendor-name="kodo" key="data-column" value="theme_id"/>
</field>
<field name="theme_description">
<extension vendor-name="kodo" key="data-column"
value="theme_description"/>
</field>
<field name="items">
<collection element-type="Item"/>
<extension vendor-name="kodo" key="inverse" value="theme"/>
</field>
</class>
</package>
</jdo>
Thanks in advance for the help.
-Tim

Abe White wrote:
The first thing to check is that you are always setting the "theme" field in
your Items. If you add an Item i to the "themes" collection of a Theme t, but
forget to also set i's "theme" field to t, then the change will never get
written to the database.
Next, make sure that whenever you set the "theme" field of an Item, you also
set
its "theme_id" field. You map both of these fields to the same column, so you
better be sure they stay in synch.
On a related note, you might try making the "theme_id" field non-persistent if
things still aren't working for you. Mapping two fields to the same column
might be causing trouble. It would be safer to make theme_id non-persistent
anyway, and to always grab the id from the Theme stored in your "theme"
field.
Better OO programming and all that, though I can see that you might have
performance issues in mind when doing it your way.
Anyway, if you find that it works when you make theme_id nonpersistent, let us
know and we'll see why the double-mapping of the column is causing problems,
and hopefully find a fix.Abe,
Thanks for the response but I'm still confused. I failed to mention that
the Item and Theme tables are in an existing schema, so as you saw in my
system.jdo, I am specifying application identity.
Since this is an existing schema, the Item table has theme_id as the
foreign key to the Theme table. So are saying that it is a problem to map
the both theme_id as a data column and a Theme object in the Item at the
same time?
I guess what I don't understand is exactly what my system.jdo should look
like to map a one-to-many relationship. In my case, from Theme (1) to Item
(many). (See my system.jdo in previous post).
Thanks
-Tim

ADF One to Many relationship

I'm a bit confused on how to create one to many relationships with ADF. Let's say I have a make and model table. One make can have many models. Now let's say I create a Business Facade like this (I'm using JavaBeans):
public Collection getMakes () { ... }
Ok, my data control now has the collection for makes. And I want to do something like this
public Collection getModels (Make make) { ... }
I can't make this work because ADF will detect it as a method accesor. How does this work?
Regards,
NÃ©stor BoscÃ¡n

Maybe looking at how TopLink does it, can help you.
Try creating TopLink objects for a master detail set of tables (dept-emp).
This will create two beans that should be similar to your beans. Look at their structure to see how they work.
The ADF TopLink workshop has the steps to show you how to do this.
http://www.oracle.com/technology/obe/obe9051jdev/ide1012/adfworkshop/buildingadfapplicationsworkshop.htm

How do I create a One to many relationship page in Dreamweaver?

How do I create a page in dreamweaver that comes up after the user logs in from the log in page that will allow the user to:
Add, change and delete in 2 tables that are in my MYSQL database that is a one to many relationship
One thing that is confusing is how the foreign key that links to the one side of the relationship is created in the many side without the user inputting the foreign key each time adding information to the many side table.
I am creating this in Dreamweaver using a MYSQL database and PHP.

>Would the following be a part of it:
>
>Outer join
Probably not. When updating/inserting/deleting from 2 tables you perform each seperately. Table updates may join two or more tables to resolve the correct row(s) but you still only update one table at a time. Procedurally you would create a transaction, update the first table, update the second table and then commit the transaction.
EDIT: Well I take back my last comment. I see that MySQL does seem to support multiple table updates. I don't use MySQL so I can't really help you on that but the MySQL manual gives pretty clear syntax.

How to change the fetch size for a one-to-many relationship

With Toplink 10.1.3, since using scrollablecursor is a prerequisites for changing the fetchsize on a query (using the setFetchSize), I am wondering if it would be possible to change the fetchsize of the query which is associated to a one-to-many relationship.
So, is this possible? How ?

In TopLink 10.1.3 you can set the fetch-size on any query, it has nothing to do with using a ScrollableCursor.
Example:
readQuery.setFetchSize(100);
To set the fetch size on a mapping query use,
mapping.getSelectionQuery().setFetchSize(100);
In 10.1.3 you can only set this in code, not currently through XML or the Mapping Workbench. In 10.1.3.1 you should be able to set the value through XML as well.

Newbie: one to many relationship SQL error

Greetings all-
This is probably a slam dunk for you JDO experts. I'm a JDO newbie, working
with an existing schema in MySQL. I have a one to many relationship between
two tables:
Table "company":
Fields:
company_id: int(11) -- primary key
name : varchar(64)
division : varchar(64)
Table "company_products"
Fields:
company_id: int(11) -- foreign key to table company
product_name: varchar(64)
product_description: varchar(64)
So, I created the corresponding classes:
public class Company {
private int companyID;
private String company_name;
private String division;
// Array of CompanyProduct
private ArrayList companyProducts;
// .. methods omitted
public class CompanyProduct {
private int companyID;
private String productName;
private String productDesc;
// Methods omitted
Then I created the "package.jdo" file:
<?xml version="1.0"?>
<jdo>
<package name="com.packexpo.db">
<class name="Company">
<extension vendor-name="tt" key="table" value="company"/>
<extension vendor-name="tt" key="pk-column" value="company_id"/>
<extension vendor-name="tt" key="lock-column" value="none"/>
<extension vendor-name="tt" key="class-column" value="none"/>
<field name="companyID">
<extension vendor-name="tt" key="data-column" value="company_id"/>
</field>
<field name="name">
<extension vendor-name="tt" key="data-column" value="name"/>
<extension vendor-name="tt" key="column-length" value="64"/>
</field>
<field name="division">
<extension vendor-name="tt" key="data-column" value="division"/>
<extension vendor-name="tt" key="column-length" value="64"/>
</field>
<field name="companyProducts">
<collection element-type="com.packexpo.db.CompanyProduct"/>
<extension vendor-name="tt" key="inverse" value="companyID"/>
</field>
</class>
<class name="CompanyProduct">
<extension vendor-name="tt" key="table" value="company_product"/>
<extension vendor-name="tt" key="pk-column" value="company_id"/>
<extension vendor-name="tt" key="lock-column" value="none"/>
<extension vendor-name="tt" key="class-column" value="none"/>
<field name="companyID">
<extension vendor-name="tt" key="data-column" value="company_id"/>
</field>
<field name="productName">
<extension vendor-name="tt" key="data-column" value="product_name"/>
<extension vendor-name="tt" key="column-length" value="64"/>
</field>
<field name="productDesc">
<extension vendor-name="tt" key="data-column"
value="product_description"/>
<extension vendor-name="tt" key="column-length" value="64"/>
</field>
</class>
</package>
</jdo>
Enhancement works fine. I successfully query and retrive Company objects
from the database, but as soon as I try to get the list of CompanyProducts,
I get an SQL Error:
javax.jdo.JDODataStoreException: [SQL=SELECT company.COMPANYPRODUCTSX FROM
company WHERE company.company_id = 82061]
E0610 Error in executeQuery()
E0606 executeQuery() error --
E0701 Error in getResult().
E0708 Command results in error - 1054 Unknown column
'company.COMPANYPRODUCTSX' in 'field list'
NestedThrowables:
com.solarmetric.kodo.impl.jdbc.sql.SQLExceptionWrapper: [SQL=SELECT
company.COMPANYPRODUCTSX FROM company WHERE company.company_id = 82061]
E0610 Error in executeQuery()
E0606 executeQuery() error --
E0701 Error in getResult().
E0708 Command results in error - 1054 Unknown column
'company.COMPANYPRODUCTSX' in 'field list'
I know i have probably set up the package.jdo file incorrectly, but I'm at a
loss for what I did wrong.
Any suggestions?
Thanks!
-Mike

Hi,
915766 wrote:
I need to write sql for below requirement:
table structure is
serial no LPN
1 4
2 4
3 6
4 6
5 6
6 3
7 3
8 3
9 1
I have to pick distinct 'LPN' like below:That sounds like a job for "GROUP BY lpn".
(any serial no can be picked for the distinct LPN)It looks like you're displaying the lowest serial_no for each lpn. That's easy to do, using the aggregate MIN function.
results needs to be as below:
serial no LPN
1 4
3 6
6 3
9 1
Please suggest with sql.Here's one way:
SELECT    MIN (serial_no)   AS serial_no
,         lpn
FROM      table_x
GROUP BY lpn
ORDER BY lpn     -- if wanted
I hope this answers your question.
If not, post a little sample data (CREATE TABLE and INSERT statements, relevant columns only), and also post the results you want from that data.
Explain, using specific examples, how you get those results from that data.
Always say which version of Oracle you're using (e.g., 11.2.0.2.0).
See the forum FAQ {message:id=9360002}

Toplink one to many relationship

I am working on DAO layer for One to many relationship
how can we get the list child objects based on parent id..
we are using toplink ...

Hi,
If you are using with JPA, try this:
em.createQuery("select c from child c where c.parent.id = :id").setParameter("id", parentObject.getId())
.getResultList();

Summarizing data in a one-to-many relationship

Post Author: Bob Amiral
CA Forum: General
I use an order tracking system that has a one to many relationship between the main order information file and the line items file. For each order, there can be one or more items in the items file. I am having no luck trying to summarize data in such a way that shows selected information from the order file with only a summary from the item file on one line. Instead, the reports expands by adding a line for each and every entry from the item file that relates to the order.
How can I summarize data from the item file to show only one line of item data in the same line as the order data?

Post Author: Charliy
CA Forum: General
Group by Order #
Suppress the Detail (and possibly the Group Header, depending on how you want it to look)
Put Running Totals in the Group Footer that reset on change of group.

One to many relationship leads to recursion?

Hi,
I've created a web services function which returns an object retrieved from a database using the persistence api (the class was generated by the Netbeans 5.5 "Entity Class from Database" feature.
I can successfully return an object which has no foreign keys. However, when I try to retrieve an entity which is on either side of a 1:N relationship, I receive a stackOverflowError.
Here's my sample schema (I'm using Derby bundled with SJAS 9 for testing)
create table Address (
   Id int not null,
   StreetName varchar(255),
   City varchar(255),
   PostalCode varchar(255),
   Party int,
   primary key (Id)
create table Party (
   Id int,
   Name varchar(255),
   primary key(Id)
alter table Address add constraint foreign key (Party) references Party;So as you can see, one Party might have many addresses.
I can retrieve either an Address or Party from the database using something like:
em.createNamedQuery("Party.findById")
   .setParameter("id", 1)
   .getSingleResult();When I try to return it, I get a stackOverflowError in the server log. I'm using the default Toplink provider so enabling full logging on this, I can see the SQL.
When retrieving an address, it selects all of the address fields and correctly binds the supplied Id value. It then performs a select on the Party table using the Address.Party value. This in turn causes it to attempt to retrieve an Address. After three queries, the error is thrown.
I can't see why the above schema should cause this problem. Where an Address is requested, I would expect it to retrieve the address fields, including the value of the Party field but not the Party object itself. On the other hand. when a Party is retrieved, I would expect it to recurse through and return a collection of Address objects.
Have I misunderstood this or am I missing some fundamental point about JAX-WS?
Thanks for your help,
-Phil

You have to set both sides of the relations...
for example to do this in a more seamless manner:
public UserProfile
     public void addLog (UserActivityLog activity)
          logs.add (activity);
          if (!equals (activity.getUserProfile ()))
               activity.setUserProfile (this);
Now this is the most primitive of ways to maintain two sided relations.
There are a lot of other patterns to get around this.
If you want to set the UserActivityLog to a specific UserProfile without
having a firm reference to ther UserProfile, you should get the object
from the database/persistenceManager... as you are using application
identity, you can do something like pm.getObjectById.
JDO does not do magic references. If you set something to null, it will
remain null until you set it.
Srini wrote:
Hi Guys
I am trying to create a one to many relationship between 2 JDOs.
UserProfile - User JDO having user info
UserActivityLog - JDO having user log info
UserProfile -- UserActivityLog
1 many
UserProfile - has a collection of UserActivityLog objects
UserActivityLog - has a reference to UserProfile
Qn 1:
I created a UserProfile along with a collection of 2 UserActivityLog
objects.
Navigation:
Now given a UserProfile object,i am able to get the UserActivityLog objects.
But given a UserActivityLog object ,i get a NULL UserProfile object.
Issues:
Why this is happening???Do i need to set the reference for "UserProfile" in
UserActivityLog before inserting???
If so,then how do i add a UserActivityLog to an existing
UserProfile???cos,if i create a UserActivityLog with reference to
UserProfile ,then it will throw a Duplicate Key violation for UserProfile as
it is already persisted in DB.
It will be great if you can direct me to some one to many relationship
examples already implemented.
Thanks
Srini
Stephen Kim
[email protected]
SolarMetric, Inc.
http://www.solarmetric.com

Confused with one to many relationship

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