Foreign key

A foreign key can be null?

If a foreign key can be duplicate?

I agree with the value null test, but not the only criterion. Your trying to insert duplicate values in the column with the primary key of the child is not the column with the foreign key table.

insert into child_t values (40,10); should work fine.

It will be useful,

Daniel

Tags: Database

Similar Questions

  • SQL statement error INSERT The conflicted with the FOREIGN KEY constraint

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  • How can I make sure that changes in a primary key (in the parent table) would also appear directly in the FOREIGN KEY in the child table?

    Forgive my question. I am very new to Oracle.

    How can I make sure that changes in the key primary supplier_id (concerning the supplier table) would also appear directly in the FOREIGN KEY (supplier_id) in the products table?

    Is that not all the primary key and FOREIGN KEY on?

    My paintings:

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    CREATE TABLE - parent provider

    (the numeric (10) of supplier_id not null,)

    supplier_name varchar2 (50) not null,

    Contact_Name varchar2 (50).

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    );

    CREATE TABLE - child products

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    CONSTRAINT fk_supplier

    FOREIGN KEY (supplier_id)

    REFERENCES beg (supplier_id)

    );

    I inserted the following text:

    INSERT INTO provider

    (supplier_id, supplier_name, contact_name)

    VALUES

    (5000, 'Apple', 'first name');

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    How to get there?

    Thanks in advance!

    Hello

    What is a foreign key in Oracle?

    A foreign key is a way to ensure referential integrity in your Oracle database. A foreign key means that the values of a table must appear also in another table.

    Ok!??

    What is now the right way to implement referential integrity in your Oracle database that the values of a table must also be included in another table?

    A foreign key referential integrity indeed enfore in ensuring that the value in the child table must have a corresponding parent key (otherwise you will encounter an error, as evidenced by "SomeoneElse"). However, it will never automatically insert a row in the other table.

    If you are looking for a solution that automatically inserts a record in the other table, maybe you should go for triggers:

    See:

  • Unwrapping names of foreign key in relational model

    Hello

    In the process of the engineer to the relational model, foreign keys get automatically wrapped. Is there somewhere a (preferably) parameter to avoid this problem? Or a function in a single step? Currently, I have to select each name and make it wider, which is very tedious. And they run again after another engineer to the relational model.

    If there is no option, I would ask for an improvement allow this. Thank you very much.

    Robert

    Sorry, a step is missing - 2.1 close design (after registration)

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    Philippe

  • correct handling of foreign keys in unique constraints for operations ON DELETE SET NULL

    During my troubleshooting at a client site, I came across an interesting setup where I would like to ask your opinion.


    Consider two tables ADTB and TBLB.

    ADTB:

    INT COLA1

    COLA2 INT

    TBLB:

    COLB1 INT

    COLA2 is COLB1 as a foreign key ON DELETE SET NULL value.

    COLA1 and COLA2 are combined into a UNIQUE for the BATTERY constraint.

    I have two records of TBLB:

    (1)

    (2)

    and two DRUM recordings:

    (1, 1)

    (2, 2)

    so far, all the constraints are valid.

    During my research, I learned that I can not put COLA2 null in ADTB for two lines at the same time:

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    -> OK

    TBLA UPDATE set COLA2 = NULL where COLA1 = 2;

    -> VIOLATED UNIQUE CONSTRAINT

    Unfortunately, it's something my application needs, anyway. In order to get this resolved, but I try to understand, what would happen if I:

    REMOVE THE TBLB;

    ?

    It should set COLA2 in ADTB "Null" on the two lines, which is not allowed due to the UNIQUE CONSTRAINT.

    Can someone shed light on this issue? Thank you.


    Yours,

    Ronny

    Unfortunately, as you say, you can't not NULL values in such a unique constraint.  It would be the same as if you had a composite primary key and try to allow one of the columns will be null in several rows with the same value in the other column.  NULL is treated as an "unknown" value, it is possible that it could be the same value (it may or may not be, but Oracle does not know), so it must assume that it might be and that's why treat it as if there is the potential for a duplicate... so it's not unique.

    In short, do not allow null values in your unique constraints.

    The default is in the drawing, not in the way that Oracle is the treatment.  Fix the design if you do not have NULL values.

    In terms of relational database design, it seems that you are trying to transform the 1:M relations M:M relations, and which requires an intermediate table if you have M:1 and 1:M between 3 tables instead.

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    Hello

    Data Modeler is a foreign key constraints do not recognize when synchronizing data with the model dictionary, although the foreign key is there (in the database that a data dictionary is read). I can't find any criterion when a foreign key is not recognized by the Data Modeler. Are there limits to the length of the attribute, or the number of columns in a foreign key, or other limitations which may lead to this behavior not to recognize a fk by Data Modeler? I have columns more than 32 characters. I compared with the fk is recognized by DM, but I can't find anything that indicates why it is not recognized.

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    Hi Robert,.

    Thanks for the comments, I logged a bug.

    Philippe

  • Delete data table Parent and child data automatically delete or the value null in the foreign key of the child table.

    Oracle 10g

    Hi gurus

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    Thanks in advance

    Hi Mit.

    example of cascade

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    )
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    delete bill
    ;
    select * from bill_item
    ;
    drop table bill_item purge
    ;
    drop table bill purge
    ;
    
    Table BILL created.
    Table BILL_ITEM created.
    1 row inserted.
    1 row inserted.
    1 row deleted.
    
    no rows selected
    
    Table BILL_ITEM dropped.
    Table BILL dropped.
    

    exemplary null

    create table employer(
      employer_id number not null primary key
    )
    ;
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      employee_id number not null primary key,
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    ;
    insert into employee values (1, 1)
    ;
    delete employer
    ;
    select * from employee
    ;
    drop table employee purge
    ;
    drop table employer purge
    ;
    
    Table EMPLOYER created.
    Table EMPLOYEE created.
    1 row inserted.
    1 row inserted.
    1 row deleted.
    
                                EMPLOYEE_ID                             EMPLOYER_ID
    --------------------------------------- ---------------------------------------
                                          1                                       
    
    Table EMPLOYEE dropped.
    Table EMPLOYER dropped.
    
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    Hi gurus

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    Appreciate if someone there explain to me...

    Concerning

    Muzz

    Hello Muzz,

    Perhaps the example of human Chen reveals a design error.
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    CREATE TABLE SCIENTIST (id people KEY PRIMARY NUMBER (id) REFERENCES, discipline VARCHAR2 (20 CHAR),...);
    CREATE TABLE POLICEMAN (id REFERENCES to KEY PRIMARY NUMBER (id), hire_date people DATE,...);

    First table = all.
    2nd: a subset of the first, with people having the profile of 'scientific '...
    3rd: a subset of the first, with people being a policeman.
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    Here is a sqlplus session illustrating; the last piece: I try inserting several lines in xxxx, only the last is accepted.

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    SQL > CREATE TABLE SCIENTIST (people of REFERENCES of KEY PRIMARY NUMBER id (id), discipline VARCHAR2 (20 CHAR));
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    SQL > CREATE TABLE POLICEMAN (people of REFERENCES of KEY PRIMARY NUMBER id (id), DATE hire_date);
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    SQL > CREATE TABLE XXXX (id PRIMARY KEY NUMBER, people_id NUMBER, any other VARCHAR2 (30 CHAR));
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    SQL > ALTER TABLE ADD CONSTRAiNT fk_xxsci FOREIGN KEY (people_id) scientific xxxx REFERENCES (id);
    Modified table.

    SQL > ALTER TABLE ADD CONSTRAiNT fk_xxpol FOREIGN KEY (people_id) police xxxx REFERENCES (id);
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    1 line of creation.

    SQL > INSERT INTO person VALUES (120, 'Mary');
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    SQL > INSERT INTO person VALUES (103, 'Tom');
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    SQL > INSERT INTO person VALUES (123, "Bruno");
    1 line of creation.

    SQL > INSERT INTO VALUES of scientific (120, 'Chemistry');
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    SQL > INSERT INTO scientific VALUES (123, 'Mathematics');
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    SQL > INSERT INTO VALUES of policeman (103, DATE ' 2001-04-01');
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    SQL > INSERT INTO VALUES of policeman (123, DATE ' 1998-07-01');
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    SQL > INSERT INTO xxxx VALUES (1, 100, "only to people");
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    SQL > INSERT INTO xxxx VALUES (1, 120, "only the learned");
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    SQL > INSERT INTO xxxx VALUES (1, 103, "only police officer");
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    SQL > INSERT INTO xxxx VALUES (1, 123, 'ok');
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    Best regards

    Bruno Vroman.

  • Creating a relationship creates no foreign key attribute (s)

    Hello

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  • PARTITION BY REFERENCE: ORA-02266 when several relatives of foreign key

    Bubble my problem down to a simple example, imagine providers of satellite TV, their programming packages, their clients and customers linking to packages.  Shouldn't be able to drop all data from a provider in one shot?

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    CONSTRAINT providers_pk PRIMARY KEY (nom_de_fournisseur)

    )

    PARTITION BY LIST (provider_name) (PARTITION provider__dflt VALUES (DEFAULT))

    /

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    REFERENCES (provider_name) providers

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    PARTITION BY REFERENCE (programming_fk1)

    /

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    (subscriber_name VARCHAR2 (50) NOT NULL)

    , provider_name VARCHAR2 (20) NOT NULL

    CONSTRAINT subscribers_pk PRIMARY KEY (subscriber_name)

    CONSTRAINT subscribers_fk1 FOREIGN KEY (nom_de_fournisseur)

    REFERENCES (provider_name) providers

    )

    PARTITION BY REFERENCE (subscribers_fk1)

    /

    CREATE TABLE subscriber_programming

    (subscriber_name VARCHAR2 (50) NOT NULL)

    , programming_name VARCHAR2 (20) NOT NULL

    CONSTRAINT Subscriber_programming_pk

    PRIMARY KEY (subscriber_name, programming_name)

    CONSTRAINT subscriber_programming_fk1 FOREIGN KEY (subscriber_name)

    Subscribers of REFERENCES (subscriber_name)

    CONSTRAINT subscriber_programming_fk2 FOREIGN KEY (programming_name)

    Programming REFERENCES (programming_name)

    )

    PARTITION BY REFERENCE (subscriber_programming_fk1)

    /

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    IN (provider_dishnetwork PARTITION, PARTITION provider__dflt)

    UPDATE INDEX

    /

    INSERT INTO suppliers (provider_name)

    VALUES ("dishnetwork")

    /

    INSERT INTO subscribers (subscriber_name, provider_name)

    VALUES ('john doe', "dishnetwork")

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    INSERT INTO programming (programming_name, provider_name)

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    /

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    -Oracle Database 11 g Enterprise Edition Release 11.2.0.4.0 - 64 bit Production

    -With options for partitioning, Real Application Clusters, Automatic Storage Management, OLAP, Data Mining and Real Application Testing

    -Linux 2.6.32 - 279.11.1.el6.x86_64 #1 SMP Sat Sep 22 07:10:26 EDT 2012 x86_64 x86_64 x86_64 GNU/Linux

    This simple demo is simply representative of course.  Our number of real paintings ~ 60, with hundreds of millions of records in a large number of tables, a tree FK covering several levels of depth, without the partition littered throughout key.  Given that the volume of data, we try hard to avoid executing DELETE, which is why I explore PARTITION migration BY reference.  The problem is not unlike the already-fixed Bug 9329773, but it is slightly different - especially that this variant is not resolved.  If there is no way that such a facility would never fly, you have any suggestions that would not involve changes to application code?  (For example, adding a partition to the tables key column kids won't fly, but I might be able to sell disabling constraints to developers.)

    After much head striking, I found the trick, by https://jonathanlewis.wordpress.com/2006/12/10/drop-parent-partition/ .  The difference of Appendix A is bold: the NOVALIDATE on subscriber_programming_fk2 and the EXCHANGE/CREATE/DROP of programming_e.

    CREATE TABLE suppliers

    (provider_name VARCHAR2 (20) NOT NULL)

    CONSTRAINT providers_pk PRIMARY KEY (nom_de_fournisseur)

    )

    PARTITION BY LIST (provider_name) (PARTITION provider__dflt VALUES (DEFAULT))

    /

    CREATE TABLE programming

    (programming_name VARCHAR2 (50) NOT NULL)

    , provider_name VARCHAR2 (20) NOT NULL

    CONSTRAINT programming_pk PRIMARY KEY (programming_name)

    CONSTRAINT programming_fk1 FOREIGN KEY (nom_de_fournisseur)

    REFERENCES (provider_name) providers

    )

    PARTITION BY REFERENCE (programming_fk1)

    /

    Subscribers of CREATE TABLE

    (subscriber_name VARCHAR2 (50) NOT NULL)

    , provider_name VARCHAR2 (20) NOT NULL

    CONSTRAINT subscribers_pk PRIMARY KEY (subscriber_name)

    CONSTRAINT subscribers_fk1 FOREIGN KEY (nom_de_fournisseur)

    REFERENCES (provider_name) providers

    )

    PARTITION BY REFERENCE (subscribers_fk1)

    /

    CREATE TABLE subscriber_programming

    (subscriber_name VARCHAR2 (50) NOT NULL)

    , programming_name VARCHAR2 (20) NOT NULL

    CONSTRAINT Subscriber_programming_pk

    PRIMARY KEY (subscriber_name, programming_name)

    CONSTRAINT subscriber_programming_fk1 FOREIGN KEY (subscriber_name)

    Subscribers of REFERENCES (subscriber_name)

    CONSTRAINT subscriber_programming_fk2 FOREIGN KEY (programming_name)

    Programming (programming_name) NOVALIDATE REFERENCES

    )

    PARTITION BY REFERENCE (subscriber_programming_fk1)

    /

    ALTER TABLE SPLIT PARTITION provider__dflt values ("dishnetwork") suppliers

    IN (provider_dishnetwork PARTITION, PARTITION provider__dflt)

    UPDATE INDEX

    /

    INSERT INTO suppliers (provider_name)

    VALUES ("dishnetwork")

    /

    INSERT INTO subscribers (subscriber_name, provider_name)

    VALUES ('john doe', "dishnetwork")

    /

    INSERT INTO programming (programming_name, provider_name)

    VALUES ('top200","dishnetwork")

    /

    INSERT INTO subscriber_programming (subscriber_name, programming_name)

    VALUES ('john doe', "top200")

    /

    CREATE TABLE programming_e AS

    SELECT * PROGRAMMING WHERE 0 = 1

    /

    ALTER TABLE programming

    Provider_dishnetwork WITH TABLE programming_e SWAP PARTITION

    /

    DROP TABLE programming_e

    /

    ALTER TABLE DROP PARTITION provider_dishnetwork UPDATE INDEX providers

    /

  • Foreign key delete rule: no matching combination does not show a difference to compare models

    Hello

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    Kind regards

    Robert

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  • Can I remove Logical columns that I will not use in the layer of presentation as the id or foreign key columns?

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    Kind regards

    Nestor

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  • Administration tool of BI - physical foreign key corresponding MDB logical join?

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  • index and foreign key

    I just read an article on the index.

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    delete this thread!

  • Term plurals changes the name of the foreign key in the relational model

    Hello

    I use a glossary with plurals for entities such as Budget turned to the budgets of the table in the relational model. Unfortunately (for me) it also changes the name of the foreign key. In the related entity, an attribute (for example) is Budget_fiscal year, I expect in the relational model, being the same, but it is transformed into budgets_fiscal_year (budgets in the plural rather than keep him in singular form).

    How can I avoid any change in the attribute names (in the process of engineering in the relational model) but always turn the names of entities from the singular to the plural names for tables?

    Thank you and best regards

    Robert

    Hi Philippe

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    I have not defined any parameter for this (intentionally). But maybe somewhere there by default. Could you tell me where the design parameters in Data Modeler to learn how to configure the definitions mentioned in 2)?

    As I'm always busy with the model of reverse engineering data, I'll wait for DM 4.1.1.888.

    Best regards

    Robert

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