One-to-many Relationships for entities with compound PK

Hi,all,
I am wondering how the behavior of a setter method would be for one side of the 1-to-many relations Base on EJB spec 2.x ,if we use the setter method to set a new collection,then the old relations are "clear" before the new relationships are established. which means the old referential integrity are removed from the respective tables in Database .But what if the referential table is with a compoud pk.Here
is one example:
Two entitybeans,say A and B , where their underlying tables are Table A and B in the Database.For A the primary key is Pk_1,but the B's primary key is (Pk_1,B1),where B1 is another column in table B. we have a setter method in entitybean A for the relationship of bean B,say setB(Collection collectionOfBs),.My questions is based on EJB spec, is container supposed to perform "clean" job, which dissassociate those old rows in table A with Table B before set the those new relationships when we call the setter to set a new relationships.
Thanks

My questions is based on EJB spec, is
container supposed to perform "clean" job, Yes, I think so. EJB spec says nothing special about compound keys in this case.
which
dissassociate those old rows in table A with Table B
before set the those new relationships when we call
l the setter to set a new relationships.
Thanks

Similar Messages

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....

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.

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.

What types of containers need to be used for one-to-many relationships

While looking at toplink examples, I noticed that synchronized containers only are being used for one-to-many relationships even though it's not required by the documentation.
Is it required?
Also how does merge affect it? I'm gettning concurrent modification exceptions from time to time, while using iterators for containers from these relationships.
Does it mean that I have to use enumeration on vectors only and toplink merge isn't atomic? So there is no isolation when toplink merges the data from unit of work into identity maps?
There is nothing about thread-safety and threading aspects of accessing containers for CollectionMapping based relationships. Please advise.

Non synchronized containers can be used but may require some extra code to handle concurrent access. If you are accessing the objects from the shared cache (not cloned in a UnitOfWork) then you will need to isolate your iteration within a synchronized block, synchronized on the collection itself, or handle the ConncurrentModificationException if they happen rarely.
Because these are shared instances of these collections other threads may be writing to them while they are being read from.
--Gordon

Persisting an instance of the many side of a in one to many relationship

It seems as if most books only tell you how to setup the relationship for a one to many relationship but seems to fail to tell you the appropriate way to persist in this relationship. So, I have a parent class with many child classes. Also, I am using services and so I am converting from Entities to Dtos and visa versa.
First, i want to insert a new child for the parent. Do I just convert the child Dto to a child entity and then persist the child entity with the reference to the parent? Then do I find the parent and add the child to the parents children so the entities are consistent?
Or do I do a find on the parent and add the child to the parents children list and the child. Will the child be persisted automatically?
With this said, what about updating a child? Do I remove the existing child and add a new one? or do I somehow find the child in the parents children set and update the info there and then somehow the child is persisted automatically? And since I am using Dto to entity, do I use a find to find the parent and then iterate through that parents children til I reach the child I modified by id somehow.
What about Many to Many relationships? With a middle join table? How does JPA know to remove a join if I change the child reference? Does it remove the old and insert the new? Or do I have to do it myself somehow. Which if the later then I really can not have a parent child Dto I really need a parent childlink table where the child is referenced by the linktable? The book I have been reading has not made this very clear.

Hello,
The relationships cascade settings determine what should happen. I would not recommend persisting a new entity that references a non-managed entity. Instead either persist the child then make the associations or find the parent, make the associations then persist the child. In the second case, you do not need to explicietly persist the child if the parent->child relationship is marked cascade persist, since it will be found on flush or commit.
Since you are using DTOs, updates require you merge the changes. You can directly merge the child, and if it has a link to its parent, modify the parent to add the child on the managed child that gets returned.
As for ManyToMany, you must modify the side that controls the relationship. So if the parent owns it, then you must modify or merge the changes into the parent for the changes to be persisted to the database. If it is bi-directional, you must modify both sides so that the cache remains consistent with the database. This should be transparent to your application, and you only need an entity for the relation table if you want to map more complex information that doesn't fit into the JPA ManyToMany options. Otherwise, JPA should handle inserting and deleting enteries to the relation table for you.
Best Regards,
Chris

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

One to Many Relationship Issue

Post Author: jmb1977
CA Forum: Formula
I am having a problem in which I have a one to many relationship with contact phone numbers and students. In other words, one student can have multiple contacts. (I work for a school district)
I made up two formulas...called Contact1Phone and Contact2Phone.
Here is the code I use to display the data:
IF {STUDCTCT.CNTNUMBER} in ["C1"] THEN STDUCTCT.CNTWPHONE
Then the other formula does the same, except uses "C2".
What I get is either C1 or C2 displays, but never both for the same student. Anyway to make this work? Any help on this would be greatly appreciated!

Post Author: jmb1977
CA Forum: Formula
I forgot to add, I do know that placing STUDCTCT.CNTNUMBER in [C1,C2] as a selection then just simply place the CNTWPHONE field into the details section of the report will give me the results. But the reason why I am trying it the other way is that I can export the data as one record per student, thus I am trying to put the fields and formulas into the group section.

One-to-many relationship within one bean

hello all,
Does S1 support a container managed one-to-many relationship to itself?
I used the verifer to verify my DD and the error is reported. (this prototype is migrated from weblogic6.1 and I use the S1 migration tool for the DD generation)
-----------------database schema-----------------
CREATE TABLE t_class_a
c_name VARCHAR2(255),
one_class_a_for_ma2918_id VARCHAR2(32), /* untruncated name: one_class_a_for_many_class_a_id */
object_id VARCHAR2(32) NOT NULL
CREATE UNIQUE INDEX t_class_a_id_PK ON t_class_a ( object_id );
ALTER TABLE t_class_a ADD ( CONSTRAINT t_class_a_id_PK PRIMARY KEY ( object_id ) USING INDEX );
ALTER TABLE t_class_a ADD ( CONSTRAINT FK_0 FOREIGN KEY ( one_class_a_for_ma2918_id ) REFERENCES t_class_a ( object_id ) );
---------------------------ejb-jar.xml------------------
<abstract-schema-name>ClassABean</abstract-schema-name>
<cmp-field>
<field-name>objectId</field-name></cmp-field>
<cmp-field>
<field-name>name</field-name></cmp-field>
<primkey-field>objectId</primkey-field>
<relationships>
<ejb-relation>
<ejb-relation-name>manyClassA_oneClassA</ejb-relation-name>
<ejb-relationship-role>
<description>optional</description>
<ejb-relationship-role-name>OneClassA-in-manyClassA_oneClassA</ejb-relationship-role-name>
<multiplicity>One</multiplicity>
<relationship-role-source>
<ejb-name>ClassAEJB</ejb-name></relationship-role-source>
<cmr-field>
<cmr-field-name>manyClassAsForOneClassA</cmr-field-name>
<cmr-field-type>java.util.Collection</cmr-field-type></cmr-field></ejb-relationship-role>
<ejb-relationship-role>
<description>optional</description>
<ejb-relationship-role-name>ManyClassA-in-manyClassA_oneClassA</ejb-relationship-role-name>
<multiplicity>Many</multiplicity>
<relationship-role-source>
<ejb-name>ClassAEJB</ejb-name></relationship-role-source>
<cmr-field>
<cmr-field-name>oneClassAForManyClassA</cmr-field-name>
</cmr-field>
</ejb-relationship-role>
</ejb-relation>
</relationships>
-----------sun-cmp-mapping.xml--------
<sun-cmp-mapping>
<schema>mySchema</schema>
<entity-mapping>
<ejb-name>ClassAEJB</ejb-name>
<table-name>T_CLASS_A</table-name>
<cmp-field-mapping>
<field-name>objectId</field-name>
<column-name>OBJECT_ID</column-name></cmp-field-mapping>
<cmp-field-mapping>
<field-name>name</field-name>
<column-name>C_NAME</column-name></cmp-field-mapping>
<cmr-field-mapping>
<cmr-field-name>manyClassAsForOneClassA</cmr-field-name>
<column-pair>
<column-name>T_CLASS_A.OBJECT_ID</column-name>
<column-name>T_CLASS_A.ONE_CLASS_A_FOR_MA2918_ID</column-name></column-pair></cmr-field-mapping></entity-mapping></sun-cmp-mapping></sun-cmp-mappings>
I beleive the migration tool missing the cmr-filed mapping for the oneClassAForManyClassA relation role.
but even if I add this mapping it still can't pass the verifiy.
So do I miss any thing or I can conclude S1 not support this one-to many self relation?
Any hint would be welcome.

It does.
There is a known problem with parsing self-referenced relationship info - the one side (with <multiplicity> Many) must be the first in the <ejb-relation> entry.
Regards,
Marina

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.

One to many relationships

Hi I have a big problem :)
I want to use one to many relationships.
One yable with primary key, foreign key view_id. The second table on the many side with primary key view_id and another primary key.
The problem is that ejbc gives the followin error:
" [java] In relationship 'ViewType-SView', role 'ViewType-Has-SView', a weblogic-relationship-role element contains the wrong number of column mappings. A single column mapping must be given for each primary key column in the bean referenced by the mapping."
And that makes no sense for me. Any ideas?

weblogic-relationship-role element column mappings should be the same as defined in
<ejb-relationship-role>
<multiplicity></multiplicity>
</ejb-relationship-role>
Erno wrote:
Hi I have a big problem :)
I want to use one to many relationships.
One yable with primary key, foreign key view_id. The second table on the many side with primary key view_id and another primary key.
The problem is that ejbc gives the followin error:
" [java] In relationship 'ViewType-SView', role 'ViewType-Has-SView', a weblogic-relationship-role element contains the wrong number of column mappings. A single column mapping must be given for each primary key column in the bean referenced by the mapping."
And that makes no sense for me. Any ideas?

One to many relationship question.

Let's say we have table1 and table2
Table1 has ID, and let's say Name for fields.
Table2 has ID, and let's say SSN for fields.
This is not so, but illustrates my points well.
Table2 has many records with the same ID, who just happen to have the same SSN. That would usually be a logical conclusion.
Table1 has only 1 of each ID in it. So you might say that ID is a foreign key in table2, except one problem. I don't think they know what primary keys are here, much less foreign keys.
Anyway, I have to write a query where I get the ID from table1 and need the SSN from table2. That's the only place in this scenario that SSN is.
My question is this - since this is a one to many relationship, yet I only need 1 result, how would I write this using the (+) way of notation? I am using 8i.
Right now, I am doing something like this, using a DISTINCT:
Select DISTINCT t1.ID, t1.Name, t2.SSN
From table1, table2,
Where t1.ID = t2.ID (+);
First of all, is this the correct way of writing it?
And second, I am wondering if, perchance for some error, there were 2 or more SSNs in table2, what would happen then? Would I get a too many rows error?
And if so, how can I trap it and possibly get just the first occurrence of it?
Is that even a sound way of doing it?
Thanks for any thoughts here.

You would need to turn your table2 into an in-line view in order to outer join to it properly. Minimally, something like:
SELECT t1.id, t1.name, t2.ssn
FROM table1 t1,
     (SELECT DISTINCT id, ssn
      FROM table2) t2
WHERE t1.id = t2.id(+)If there may be multiple ssn in t2 for a single id, you will need to determine which one you want to keep and use something like:
SELECT t1.id, t1.name, t2.ssn
FROM table1 t1,
     (SELECT id, ssn
      FROM (SELECT id, ssn,
                   ROW_NUMBER() OVER (PARTITION BY id,
                                      ORDER BY column_that_makes_it_first) rn
            FROM table2)
      WHERE rn = 1) t2
WHERE t1.id = t2.id(+)This should work on 8.1.7.4 Enterprise Edition. If you have a different version, then the analytic function may not work so you would need something more like:
SELECT t1.id, t1.name, t2.ssn
FROM table1 t1,
     (SELECT id, ssn
      FROM (SELECT id, ssn, rownum rn
            FROM (SELECT id, ssn,
                  FROM table2
                  ORDER BY id, column_that_makes_it_first))
      WHERE rn = 1) t2HTH
John

One-to-many Relationships for entities with compound PK

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