Necessary to have foreign keys ?

Dear All,
We have a oracle database, in which there is no foreign key constraints defined. But we are able to join the tables with the appropriate columns and getting the output of the query perfectly.
Now, is that mandatory to have foreign key columns defined or the current design is fine. Please help me in this, by discussing the advantages and disadvantages.
Thanks in advance.
Anand.

Best practice would absolutely be to have foreign keys in an OLTP system.
Without foreign keys, you are guaranteed to have data that violates referential integrity eventually. Unless you happen to be lucky enough to work on an application that will never have bugs, you need Oracle to enforce referential integrity.
Without foreign keys, your data model is much harder to understand. That means that when new developers come on the project, when people want to point various tools at the database, etc. those people and tools will not be able to use foreign keys to determine how the tables relate. That inevitably means that it will take them far longer to get up to speed and they are far more likely to make errors. If you ever point an automated tool at the database to generate an ERD, that tool will be nearly useless since it can't figure out how the tables relate.
Without foreign keys, you're depriving the optimizer of information that may allow it to generate better plans.
Yes, you need to index foreign keys in the child table, but you almost certainly need these indexes for queries anyway. Other than that, there are really no downsides. Yes, Oracle has to do a minute amount of work to verify the foreign key during DML, but it will be far more efficient for Oracle to do this than for your application to do it.
Justin

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In ADF how can i insert data in multiple table if they have foreign key

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Hello,
Still no luck.I am surely doing silly mistakes.Anyway,Here are my workings-
1> student_mst (id(pk),studentname) and student_guard_mst(id(fk),guardianname)
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Copying tables that have Foreign Keys

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stu_school
PK_ID
FK_YEAR
FK_SCHOOL
FK_GRADE_LEVEL
year
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IMHO -- Mark D Powell --

Why can't global temporary tables have foreign keys?

Hi,
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thanks,
Pete

Adding a foreign key to an access table

I have set up two tables in access and I am using SQL insert
with the form to populate the database. When I “submit”
the form I receive the following error:
Element CUST_ID is undefined in CUSTOMER_INFO.
The error occurred in
C:\Inetpub\wwwroot\spl_web_site\public_records\order_insert.cfm:
line 23
21 : <cfquery datasource="#odbc_datasource#"
name="desc">
22 : insert into rec_results (customer_info.cust_id,rec_desc)
23 : values('#customer_info.cust_id#',
24 : '#rec_desc#')
25 : </cfquery>
How do I get cust_id into the second table to be used as the
foreigh key when it “has not been created (defined)” in
the first table?

If your cust_id is an autonumber primary key field in your
first table, then you will have to create that record first, then
retrieve the primary key value to be used as your foreign key in
your second table, especially if you have foreign key constraints
on the table. This is normal relational database behavior, since it
isn't really possible to have a child if there is no parent. In
this case, you will need some sort or SELECT between your two
inserts in order to determine the newly created cust_id. Or, you
may need some other means of gerating your unique PK value for
cust_id outside of Access. If you do the SELECT method, you would
do something like SELECT MAX(cust_id) FROM customer_info (assuming
that cust_id is generated sequentially), and you should enclose all
three database transactions within CFTRANSACTION tags so that you
don't accidentally grab the wrong cust_id from another simultaneous
transaction.
Phil

Foreign keys in source tables (sybase database)

Hi,
Foreign key / primary key constraints are not captured / converted in oracle model nor they are generated.
I am migrating sybase database tables to oracle. These tables have foreign keys, but while capturing and then converting the table to oracle model and then generating, these foreign keys are not present in the ddl script.
In the source connection ( in the tool) to the sybase database, these keys are shown,
and logically when the generation is done for table, the foreign / primary key syntax should be present in the ddl generated
Am more worried about the foreign key not getting converted
Please help
Regards

Hello,
do you have a very simple example showing this behaviour ?
What is your sybase version ? And what about Sqldev version ?
Do you tested migration with offline method ?
As testcase, a emp and dept schema with foreign key should be ideal.
Thanks
Regards,
Marcello

Foreign Key reference

Hi all,
I have two tables called PATIENT and PERSON. All persons are not patients but all patients are persons. Now how to define the relation between the two tables? Should PATIENT have foreign key reference to PERSON or should PERSON have foreign key reference to PATIENT?
thanks in advance.

It really depends what you want to accomplish. If 99% of people are patients, then it may be better to merge these two tables into one. If just a few people are patients, that a separate patient table is o.k. with the same key as in person table.

How we relate two tables using foreign key(fk)?

hi to all,
what are the conditions has to follow to relate two tables.I.e.,
the two tables have same primary keys(pk). if we relate these two tables in one table the pk and fk will be the same then how that table in active.

Hi
To relate two tables..we have foreign key relationship.
In one table v have primary key and in the second table, the same key is foreign key for that table..
To relate two tables, we can use JOINS
If there is already a suitable foreign key between two tables used in the view, these tables can be linked with a join condition from this foreign key.
Create a view on tables TAB1 and TAB2. TAB1 is the primary table of the view. TAB2 is the secondary table of the view. TAB1 is the check table for TAB2. The foreign key fields are assigned to the check table fields as follows:
TAB1-FIELD_A assigned to TAB2-FIELD_1
TAB1-FIELD_A assigned to TAB2-FIELD_1
The join condition of the view generated from the foreign key is then:
CREATE VIEW ... AS SELECT ... WHERE TAB2-FIELD_1 = TAB1-FIELD_A AND TAB2-FIELD_2 = TAB1-FIELD_B.
Join conditions can also be copied from generic and constant foreign keys. If a constant is assigned to a field in the foreign key, it is also assigned to the field in the join condition. There is no join condition for a generic relationship in the foreign key.
The foreign key between tables TAB1 (check table) and TAB2 (foreign key table) is defined as follows:
TAB1-FIELD_A assigned to TAB2-FIELD_1
TAB1-FIELD_B generic
TAB1-FIELD_C assigned to constant C
The join condition for the view generated from the foreign key is in this case:
CREATE VIEW ... AS SELECT ... WHERE TAB2-FIELD_1 = TAB1-FIELD_A AND TAB2-FIELD_2 = C.
Hope it helps
Reward if useful.

Hiding foreign keys

Is there an option to hide foreign keys in Relational model? I have more then 1000 keys in model and all those lines in diagrams slows program.
In the part of the model where are no foreign keys the transitions and scrolling are very smooth.
Thanks!

The problem is that you may want to include tables (or entities in ER diagrams) that have multiple foreign keys, and you only want to include some of the foreign keys on the diagram.
Example:
If the diagram contains tables A, B and C that all have foreign keys between them, you may want to show all foreign keys to and from table B but not the ones between A and C.
/ Marc de Oliveira

How can I have multiple instances of a column that itself holds a foreign key reference?

I am new to Visual Studio so to start learning it I first of all downloaded a sample available at https://code.msdn.microsoft.com/ADPNET-Entity-Framework-2d1160cb and started working around it. Since I have fairly good knowledge of VB6 and SQL it did
not take much time for me to understand the whole pattern the sample is based on. Had Microsoft given a detail explanation or a walk through of the sample it would have been much easier to understand the basics. However, I somehow managed to work around it
and have build a small desktop application in wpf using Entity Framework and MVVM. But a point has come where I have got completely stuck up finding no way out. The problem is as under:
I have two tables. 1 Advocate and 2 Party. Table Advocate would contain names of advocates and would have a primary key. Similarly Party would have names and their respective primary keys.
Then I have another two tables 1. Case and 2 CaseDetail. Table Case would simply hold three columns: 1. CaseId 2. CaseNo and 3. Year. Table CaseDetail would have CaseDetailId as a primary key the CaseId as a Foreign Key. Now what I need is that a particular
case could have multiple advocates and multiple petitioners. So the table CaseDetail would have two columns to hold advocateId and PartyId as a Foreign Keys.
If you look at the sample referred above you would not find how to deal with such a case. When I follow the pattern of the sample I get host of design time and runtime errors.
Therefore, please suggest what strategy should be adopted in a scenario described above while developing WPF application using Entity Framework and MVVM.

I am new to Visual Studio so to start learning it I first of all downloaded a sample available at https://code.msdn.microsoft.com/ADPNET-Entity-Framework-2d1160cb and started working around it. Since I have fairly good knowledge of VB6 and SQL it did not
take much time for me to understand the whole pattern the sample is based on. Had Microsoft given a detail explanation or a walk through of the sample it would have been much easier to understand the basics. However, I somehow managed to work around it and
have build a small desktop application in wpf using Entity Framework and MVVM. But a point has come where I have got completely stuck up finding no way out. The problem is as under:
I have two tables. 1 Advocate and 2 Party. Table Advocate would contain names of advocates and would have a primary key. Similarly Party would have names and their respective primary keys.
Then I have another two tables 1. Case and 2 CaseDetail. Table Case would simply hold three columns: 1. CaseId 2. CaseNo and 3. Year. Table CaseDetail would have CaseDetailId as a primary key the CaseId as a Foreign Key. Now what I need is that a particular
case could have multiple advocates and multiple petitioners. So the table CaseDetail would have two columns to hold advocateId and PartyId as a Foreign Keys.
If you look at the sample referred above you would not find how to deal with such a case. When I follow the pattern of the sample I get host of design time and runtime errors.
Therefore, please suggest what strategy should be adopted in a scenario described above while developing WPF application using Entity Framework and MVVM.

Does a foreign key have to be a primary key

Hey all.I was checking on the database code written by sambapos.To my surprise, I found a foreign key that is not a primary key anywhere.
Is that possible?
If, so why?
I am really astonished.

Limitations and Restrictions
A foreign key constraint does not have to be linked only to a primary key constraint in another table; it can also be defined to reference the columns of a UNIQUE constraint in another table.
When a value other than NULL is entered into the column of a FOREIGN KEY constraint, the value must exist in the referenced column; otherwise, a foreign key violation error message is returned. To make sure that all values of a composite foreign key constraint
are verified, specify NOT NULL on all the participating columns.
FOREIGN KEY constraints can reference only tables within the same database on the same server. Cross-database referential integrity must be implemented through triggers. For more information, see
CREATE TRIGGER (Transact-SQL).
FOREIGN KEY constraints can reference another column in the same table. This is referred to as a self-reference.
A FOREIGN KEY constraint specified at the column level can list only one reference column. This column must have the same data type as the column on which the constraint is defined.
A FOREIGN KEY constraint specified at the table level must have the same number of reference columns as the number of columns in the constraint column list. The data type of each reference column must also be the same as the corresponding column in the column
list.
The Database Engine does not have a predefined limit on either the number of FOREIGN KEY constraints a table can contain that reference other tables, or the number of FOREIGN KEY constraints that are owned by other tables that reference a specific table.
Nevertheless, the actual number of FOREIGN KEY constraints that can be used is limited by the hardware configuration and by the design of the database and application. We recommend that a table contain no more than 253 FOREIGN KEY constraints, and that it
be referenced by no more than 253 FOREIGN KEY constraints.
FOREIGN KEY constraints are not enforced on temporary tables.
If a foreign key is defined on a CLR user-defined type column, the implementation of the type must support binary ordering. For more information, see
CLR User-Defined Types.
A column of type varchar(max) can participate in a FOREIGN KEY constraint only if the primary key it references is also defined as type
varchar(max).
Read this article
http://msdn.microsoft.com/en-us/library/ms189049.aspx
Regards, Ashwin Menon My Blog - http:\\sqllearnings.com

Building relationships that have no foreign key

Hi,
I have a situation where the database team have provided me a schema
something like that shown below:
PERSON
|========================================|
| PK | NAME | SSNUM | MGR |
|========================================|
| 1 | john | 123-45-6789 | 3 |
| 2 | fred | 987-65-4321 | 3 |
| 3 | alice | 111-22-3333 | NULL |
| ... |
|========================================|
COMPANY
|=================|
| PK | NAME |
|=================|
| 1 | acme |
| 2 | bcme |
| 3 | ccme |
| |
|=================|
ATTRIBUTE
|========================================|
| PK | SOURCE_ID | SOURCE_TYPE | VALUE |
|========================================|
| 1 | 1 | P | one |
| 2 | 1 | C | two |
| ... |
|========================================|
PERSON and COMPANY are application objects. A PERSON or a COMPANY can
have an ATTRIBUTE tagged to it. Now, there is not a foreign key
relationship from PERSON/COMPANY to ATTRIBUTE. The relationship can be
derived by understanding that ATTRIBUTE.SOURCE_ID is the PK value for
either PERSON or COMPANY, and ATTRIBUTE.SOURCE_TYPE states whether its a
PERSON (P) or COMPANY (C).
The database guys say this is a common approach to modelling data that
is not a "first order" property of a class, which I guess may be up for
debate. In any case....
I can't model this using objects and relationships using KODO. So, my
question is, how would you approach this?
Thanks,
Mike.
PS As an aside, if there was a way in the JDO metadata to "hardcode" a
value for one or more of the columns in a foreign key relationship, it
would help a lot. Then I could build a navigable link from PERSON to
ATTRIBUTE, where the SOURCE_ID data column is PERSON.PK and the
SOURCE_TYPE is the string literal 'P'.

That certainly is a unique problem... and certainly not a sort of model I
would encourage...
however, you should be able to accomplish this in Kodo with a non-direct
relationship... i.e. Attributes has a reference-id not a reference. So
Attribute may say look like this:
private int referenceId = -1;
private char type;
public void getSource ()
Object oid = null;
if (referenceId < 0)
     return null;
switch (type)
case 'P':
     oid = new PersonId (referenceId);
     break;
case 'C':
     oid = new CompanyId (referenceId);
     break:
default: return null;
return JDOHelper.getPeristenceManager (this).getObjectById (oid, true);
public void setSource (Person p)
PersonId pid = (PersonId) JDOHelper.getObjectId (p);
refernceId = pid.id;
type = 'P';
Now this would get a little more complicated for objects which
haven't been made persistent, but can simply be accomplished by using
javax.jdo.InstanceCallbacks and preStore () and using a transient field
Object source. Using non-application identity, would require casting oids to
our ObjectIds.Id (in our JavaDoc). Actually, as I think about it, it may
be better to do this all in a transient state:
public Attribute
     private transient Object src;
     private int referenceId;
     private char type;
     public void setSource (Person p)
          src = p;
     public Object getSource ()
          if (src != null || JDOHelper.getPersistenceManager (this) == null)
               return src;
          /// same as previous example
          return JDOHelper.getPersistenceManager (this).getObjectById (oid);
     public void preStore () // instancecallbacks
          PersonId id = (PersonId) JDOHelkper.getObjectId (src);
          referenceId = id.id;
          type = 'P';
Again this isn't 100% solid code but a suggestion to get you started on
your problem.
While 3.0 will support more complex mappings, it won't get around the
multiple types per field problem... but this could be solved via
interfaces (e.g. public interface AttributeSource), though I'd have to
defer to our 3.0 architect on that one.
On Fri, 14 Feb 2003 16:15:04 +0200, Mike Hogan wrote:
Hi,
I have a situation where the database team have provided me a schema
something like that shown below:
PERSON
|========================================|
| PK | NAME | SSNUM | MGR |
|========================================|
| 1 | john | 123-45-6789 | 3 |
| 2 | fred | 987-65-4321 | 3 |
| 3 | alice | 111-22-3333 | NULL |
| ... |
|========================================|
COMPANY
|=================|
| PK | NAME |
|=================|
| 1 | acme |
| 2 | bcme |
| 3 | ccme |
| |
|=================|
ATTRIBUTE
|========================================|
| PK | SOURCE_ID | SOURCE_TYPE | VALUE |
|========================================|
| 1 | 1 | P | one |
| 2 | 1 | C | two |
| ... |
|========================================|
PERSON and COMPANY are application objects. A PERSON or a COMPANY can
have an ATTRIBUTE tagged to it. Now, there is not a foreign key
relationship from PERSON/COMPANY to ATTRIBUTE. The relationship can be
derived by understanding that ATTRIBUTE.SOURCE_ID is the PK value for
either PERSON or COMPANY, and ATTRIBUTE.SOURCE_TYPE states whether its a
PERSON (P) or COMPANY (C).
The database guys say this is a common approach to modelling data that
is not a "first order" property of a class, which I guess may be up for
debate. In any case....
I can't model this using objects and relationships using KODO. So, my
question is, how would you approach this?
Thanks,
Mike.
PS As an aside, if there was a way in the JDO metadata to "hardcode" a
value for one or more of the columns in a foreign key relationship, it
would help a lot. Then I could build a navigable link from PERSON to
ATTRIBUTE, where the SOURCE_ID data column is PERSON.PK and the
SOURCE_TYPE is the string literal 'P'.--
Stephen Kim
[email protected]
SolarMetric, Inc.
http://www.solarmetric.com

Field MATNR does not have a foreign key; as a result no intervals are allow

Hello,
We are having ROH and FERT material , in that we were entered the wrong Item category group , we need to change the
Item category group through mass posting through MM17. we are getting below given error
"Field MATNR does not have a foreign key; as a result no intervals are allowed"
Message no. M&132
Diagnosis
You have either specified an interval such as from 1 to 10 or M* for a field, or you have left the field blank, corresponding to the interval *. However, since there is no foreign key for this field, the system cannot resolve the interval into valid single values.
Procedure
Enter only single values for this field.
We have checked the the structure MPGD_MASS in SE11, and here foreign key mark is tciked in "entry help/ check.
How to solve this error.
Regards
sapman man

how did you then proceed, on the selection screen:
did you just use the change tab or did you work as well or only at the create tab?
What did you enter in the selection?
(...because I just tried a mass change without specying a material number and do not get such message)

VLD-0203: Foreign key ENC_COLLECTION_TYPES_1 does not have a referenced col

When I try to deploy a source table a got the error.
VLD-0203: Foreign key ENC_COLLECTION_TYPES_1 does not have a referenced column.
All foreign keys must have referenced columns. Complete the foreign key definition by referencing a column
How can I fix this issue ??

Hi,
Just refer to the correct column for the FK created (you need to have a parent table available/deployed first before this is deployed). Since you are deploying the source table which will create the same in DB you have to make sure the keys are set correctly and the parent table is already available in DB.
We generally create the tables first in DB and then use the import functionality to bring it into OWB repository.
Regards,
Bharadwaj Hari

I need to have multiple foreign keys on one column, can Designer do this?..

Basically I've a table that needs to link to three other tables. As far as I can tell Designer will only let me have the foreign keys on seperate columns;
Column_1 - FK1
Column_2 - FK2
Column_3 - FK3
I think it's a much better database design is to have all three link to one column and have a Type column denoting which table to references
Column_1 - FK1, FK2, FK3
Column_2 - Type (FK1, FK2, FK3)

Can you tell us more about the problem you're trying to solve?
Thanks, George

Necessary to have foreign keys ?

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