Two foreign keys of a table in a single column

Similar Questions

• Two foreign keys to a primary key

  I can't display information to two foreign keys in my table. My purpose is to display the name and surname of a project manager and account manager. I have a "Jobs" table that is linked to a table 'employees '.
  
  Jobs
  ProjectMgrID
  AcctMgrID
  
  Employees
  EmployeeID
  LastName
  FirstName
  
  The ProjectMgrID (fk) and the AcctMgrID (fk) are related to the EmployeeID (pk). When I create a query, I do not know how to display the first name and the name of the fields for both. It only allows me to add them once and when I add both times, it just displays the same information twice.
  
  Help, please!

  Welcome to the forum!

  Looks like you will have to join EMPLOYEES twice.

  Something like the following:

  SELECT  e1.firstname
  ,       e1.lastname
  ,       e2.firstname
  ,       e2.lastname
  FROM    jobs
  JOIN    employees e1    ON e1.employeeid = jobs.projectmgrid
  JOIN    employees e2    ON e2.employeeid = jobs.acctmgrid
  ;
  

• A table with two foreign keys

  Hi all
  
  I need to create a table (mytable) filled from 2 different tables, for example, table1 and table2
  
  When the rows of the table (mytable) comes from the first table (table1) columns in mytable (foreign key to the second table) are nulled, when they come (foreign key) column in the second table (table2)
  the first table) are cancelled as well.
  
  In terms of performance, architecture is valid, in other words, create a foreign key 2 on mytable and consequently, (the composite foreign key in this table are null according to whether they belong to the first or the second table)?
  
  Thanks in advance for any help
  
  I hope to clear

  As promised,

  mhouri.world > create table p as select * from all_users;
  
  Table created.
  
  mhouri.world > alter table p add constraint p_pk primary key (user_id);
  
  Table altered.
  
  mhouri.world > create table c (user_id references p, name varchar2(30));
  
  Table created.
  
  mhouri.world > select min(user_id),max(user_id) from p;
  
  MIN(USER_ID) MAX(USER_ID)
  ------------ ------------
             0           72                                                       
  
  mhouri.world > insert into c (user_id, name) values (0, 'test without index');
  
  1 row created.
  

  Thanks to the autonomous operation I simulates the effect of two users working on the same parent/child table

  (a) first of all, without any index covering the FK on the child table

  (b) second with a function based index on the FK column (note the desc clause in the definition of the index)

  (c) and finally with an index b-tree on the FK columns

  case (a)

  mhouri.world > declare
    2  pragma autonomous_transaction;
    3  begin
    4  delete from p where user_id = 72;
    5  commit;
    6  end;
    7  /
  declare
  *
  ERROR at line 1:
  ORA-00060: deadlock detected while waiting for resource
  ORA-06512: at line 4 
  
  mhouri.world > rollback;
  
  Rollback complete.
  

  case (b)

  mhouri.world > create index fbi_c_fk on c (user_id desc);
  
  Index created.
  
  mhouri.world > insert into c (user_id, name) values (0, 'test with fbi index');
  
  1 row created.
  
  mhouri.world > declare
    2  pragma autonomous_transaction;
    3  begin
    4  delete from p where user_id = 72;
    5  commit;
    6  end;
    7  /
  declare
  *
  ERROR at line 1:
  ORA-00060: deadlock detected while waiting for resource
  ORA-06512: at line 4 
  
  mhouri.world > rollback;
  
  Rollback complete.
  

  case (c)

  mhouri.world > create index btree_c_fk on c (user_id);
  
  Index created.
  
  mhouri.world > insert into c (user_id, name) values (0, 'test with b-tree index');
  
  1 row created.
  
  mhouri.world > declare
    2  pragma autonomous_transaction;
    3  begin
    4  delete from p where user_id = 72;
    5  commit;
    6  end;
    7  /
  
  PL/SQL procedure successfully completed.
  

  Only the index b-tree covered with success the threat of the deadlock in key foreign unidexed

  Best regards

  Mohamed Houri

• Two foreign keys

  Hi, I would like to create a table with two strangers with the same name.
  
  I have a first table named ' * registry * ' with a column named "* id_registry *" PK, and another called 'friends' table with two columns "* id_res *" and "* id_friends." Now I would like to id_res and id_friends should be CF and have the same id_registry PK as references.
  I tried this way:
  ALTER TABLE friends add friends COSTRAINT: FK REFERENCES FOREIGN KEY (id_res, id_friends) anagrafica (id_registry); but I got an error like this: ORA-02256.
  
  Is possible to do?

  You must create two foreign keys separated like that.

  ALTER TABLE friends ADD CONSTRAINT friends_FK1 FOREIGN KEY (id_res) REFERENCES anagrafica (id_registry);
  
  ALTER TABLE friends ADD CONSTRAINT friends_FK2 FOREIGN KEY (id_friends)  REFERENCES anagrafica (id_registry);
  

• foreign key referencing the table in different schema

  I create a foreign key for the table in the schema A a table to diagram B.
  
  I do that by grant references (column name) on the name of the table to username;
  
  
  is there any drawback/disadvantage in the creation of foreign keys referencing tables in another schema?

  Not as such, no.

  Generally, you want to check a second time when you are in this kind of situation that the two tables really belong in different schemas. It should be relatively rare to find a child table that belongs to a different schema than the parent. Sometimes, but it should be an exception, not the rule.

  Justin

• Is a foreign key MUST have a UNIQUE or PK column as a reference?

  First I tried, from what I saw Yes it must be Unique or PK. Secondly, I am pretty sure that I read somewhere where there are PK or unique. Thirdly, I checked oradocs and other pages, the thing ends, I owe an answer

  Constraint foreign key (also called a constraint referential integrity) designates a column as a foreign key and establishes a relationship between this foreign key and a primary or unique key specified, called the referenced key.

  
  

  This implies, but does not explicitly specify that it MUST be a PK or a SINGLE.

  
  

  Basically I want a simple yes/no answer just to give me some peace of mind. I don't want to waste any time, but changes to the oracle from time to time, and I'd rather have a confirmation from someone with more knowledge/experience.

  
  

  Thank you!

  Yes.

  This same document you are referencing tells you what are the rules for the creation of a foreign key.

  Data integrity

  Foreign key constraints

  Whenever two tables have one or more common columns, Oracle database can apply the relationship between the two tables with a foreign key, also called a referential integrity constraint constraint. The constraint requires that for each value in the column on which the constraint is defined, the value in the other specified that another table and column must match. An example of a referential integrity rule is that an employee may work for only one Department.

  Table 5-2 lists the terms associated with referential integrity constraints.

  Table 5-2 referential integrity constraint conditions

  Term

  Definition

  Foreign key

  The column or set of columns included in the constraint definition that refers to a key that is referenced. For example, the department_id column employees is a foreign key that refers to the department_id column of departments . Foreign keys can be described as several columns. However, a composite foreign key must refer to a primary or unique key with the same number of columns and the same types of data.

  The value of the foreign keys can be either the primary or unique key value referenced or be null. If any column of a composite foreign key is null, then the portions not null the key do not match any corresponding part of a parent key.

  Referenced key

  The unique key or the primary key of the table referenced by a foreign key. For example, the department_id column departments is the key referenced to the department_id column of employees .

  Table dependent or child

  The table containing the foreign key. This table is based on the values present in the primary or unique key referenced. For example, the employees table is a child of departments .

  Referenced or the parents table

  The table that is referenced by the foreign key of the child table. It is the key to this table reference that determines whether specific inserts or updates are allowed in the child table. For example, the departments table is a parent of employees .

  The first three terms defined in the table EXPLICITLY State references to the 'core' or 'unique' keys to the parent.

  The doc also refers to the Application Developer Guide:

  Maintaining the integrity of the data in Database Applications

  Foreign key references a primary key by default

  If the list of columns is not included in the REFERENCES option when you set a FOREIGN KEY constraint (simple or composite column), then Oracle database assumes that you want to reference the primary key of the specified table. You can also explicitly specify the columns to reference the table parent in parentheses. Oracle database checks automatically to check this list of column refers to a primary or unique to the parent table key. If it isn't, an informative error is returned.

  That the entire paragraph is as explicitly as it gets.

  No list of columns? Oracle then checks for a primary key.

  There is a list of columns? Then Oracle 'control to verify this list of column made reference to a primary or unique key'...

• Questions about the creation of a foreign key on a table

  Hello @ll,
  
  during an update of the database, I lost a foreign key between two tables. The tables are called werteart and werteartarchiv_pt. Because of its size, werteartarchiv_pt is a partitioned table. The missing foreign key was a constraint on werteartarchiv_pt table referencing werteart.
  
  Some statistics on the size of the mentioned tables:
  werteart 22 MB
  werteartarchiv_pt 223 GB
  werteartarchiv_pt (Index) 243 GB
  
  I tried to create the foreign key again but it failed with the following error (apologies for the German error message):
  
  sqlplus ORA-00604: Fehler auf rekursiver SQL-ebony 1
  sqlplus ORA-01652: Temp-Segment kann nicht um 128 in Tablespace TEMPS00 judgements
  
  The statement that I used:
  
  ALTER table werteartarchiv_pt
  Add constraint werteartarchiv_pt_fk1
  foreign key (rail, werteartadresse, merkmale)
  Reference werteart (rail, werteartadresse, merkmale)
  on delete cascade
  at the delayed start can be delayed;
  
  So, the problem seems to be that Oracle needs a lot of temporary tablespace to generate foreign key and I do not know how and why.
  
  My questions now are, and I hope that someone is there who can answer all or part of it:
  
  (1) why Oracle should temporary tablespace to create the foreign key? The foreign key uses the same columns as the primary key.
  
  is 2 (a) possible to change the statement without using the temporary tablespace?
  
  2 (b) if it is not possible to avoid the use of temporary storage space, is there a formula how to calculate the necessary temporary tablespace?
  
  (3) is it possible to modify data in tables while the foreign key is created or is the whole table locked during the process?
  
  Any help or advice is appreciated.
  
  Kind regards
  Bjoern

  RollinHand wrote:
  My questions now are, and I hope that someone is there who can answer all or part of it:

  (1) why Oracle should temporary tablespace to create the foreign key? The foreign key uses the same columns as the primary key.

  Because it is data validation to ensure that the foreign key are violated. If you had specified NOVALIDATE ACTIVATE in its creation then the existing data in the table should be checked and the statement must fill out instantly (future data added is enabled by the constraint).

  http://download.Oracle.com/docs/CD/B28359_01/server.111/b28310/general005.htm

  Search for "Enable Novalidate constraint State"

• Online syntax to create Foreign key with Alter Table statement

  I am a pretty meticulous reader. That being said, from the 4 texts that I read to start to learn SQL, I do not remember and do more that probably not, find a syntax online for the creation of a CF with the statement alter table.

  Just something I thought while I was reading.

  Is there a such syntax?

  And if so someone can give me direction on my code?

  ALTER table emp4 change employee_id key foreign employees of references (employe_id);

  It gives me the option error invalid alter table.

  Any idea would be appreciated.

  Thank you.

  rp0428 wrote:

  A foreign key is a constraint, you must use ADD CONSTRAINT.

  Thare is more than one way to skin a cat:

  SQL > create table tbl (id number, name varchar2 (10))
  2.

  Table created.

  SQL > alter table tbl adds (foreign key references emp (empno))
  2.

  Modified table.

  SQL > select constraint_name,.
  2 constraint_type
  3 from user_constraints
  4 where table_name = 'TBL '.
  5.

  CONSTRAINT_NAME C
  ------------------------------ -
  SYS_C0021920 R

  SQL > drop table tbl purge
  2.

  Deleted table.

  SQL > create table tbl (id number, name varchar2 (10))
  2.

  Table created.

  SQL > alter table tbl change (foreign key references emp (empno))
  2.

  Modified table.

  SQL > select constraint_name,.
  2 constraint_type
  3 from user_constraints
  4 where table_name = 'TBL '.
  5.

  CONSTRAINT_NAME C
  ------------------------------ -
  SYS_C0021921 R

  SQL >

  SY.

• How do I change or add constr. foreign key to the table whose children or data lines

  Hello
  
  I have a table with the name of Department in which the DEPTNO column is a column of data and primary key in it for all columns. Now, I have a table EMP where DEPTNO column is not having any constraints, including constraint foreign key also. I now have data in the EMP table for all columns. I would now add the DEPTNO column foreign key constraint in the EMP table that references the column DEPTNO in DEPT table. Both the table have not all null values.
  
  I need to add the foreign key without removing the data in the EMP table.
  
  
  Please advice.
  
  Kind regards
  Alriq

  In addition, if you have pre-existing data that will never have a parent record but you want to ensure that any NEW data is consistent with the FK constraint you can always create it with the NOVALIDATE option:

  SQL> CREATE TABLE EMP_BKP AS SELECT * FROM SCOTT.EMP;
  
  Table created.
  
  SQL> CREATE TABLE DEPT_BKP AS SELECT * FROM SCOTT.DEPT;
  
  Table created.
  
  SQL> DELETE FROM DEPT_BKP WHERE DEPTNO=10;
  
  1 row deleted.
  
  SQL> ALTER TABLE DEPT_BKP ADD CONSTRAINT DEPT_BKP_PK PRIMARY KEY(DEPTNO);
  
  Table altered.
  
  SQL> ALTER TABLE EMP_BKP ADD CONSTRAINT DEPT_FK FOREIGN KEY(DEPTNO) REFERENCES DEPT_BKP(DEPTNO);
  ALTER TABLE EMP_BKP ADD CONSTRAINT DEPT_FK FOREIGN KEY(DEPTNO) REFERENCES DEPT_BKP(DEPTNO)
                                     *
  ERROR at line 1:
  ORA-02298: cannot validate (TEST_USER.DEPT_FK) - parent keys not found
  
  SQL> ALTER TABLE EMP_BKP ADD CONSTRAINT DEPT_FK FOREIGN KEY(DEPTNO) REFERENCES DEPT_BKP(DEPTNO) NOVALIDATE;
  
  Table altered.
  
  SQL> INSERT INTO EMP_BKP(EMPNO,ENAME,DEPTNO) VALUES(9999,'Test Emp',10);
  INSERT INTO EMP_BKP(EMPNO,ENAME,DEPTNO) VALUES(9999,'Test Emp',10)
  *
  ERROR at line 1:
  ORA-02291: integrity constraint (TEST_USER.DEPT_FK) violated - parent key not found
  
  SQL> SELECT * FROM EMP_BKP WHERE DEPTNO = 10 ORDER BY EMPNO;
  
       EMPNO ENAME      JOB              MGR HIREDATE                   SAL       COMM     DEPTNO
  ---------- ---------- --------- ---------- ------------------- ---------- ---------- ----------
        7782 CLARK      MANAGER         7839 06/09/1981 00:00:00       2450                    10
        7839 KING       PRESIDENT            11/17/1981 00:00:00       5000                    10
        7934 MILLER     CLERK           7782 01/23/1982 00:00:00       1300                    10
  

• primary key for a table with only 1 column

  I create a temporary table in my procedure and there is only a single column in it. I'll eventually use this temporary table in a join. Does make sense to create a primary key for this temporary table? It will make my join run faster? In other words, oracle automatically sorts and keeps the table column is the fact that if a primary key or index is created? I use 10g - 10.2.0.3.0

  The data table is not indexed.

  Oracle will probably make a hash join.

  Have you tried just current execution Plan for your query to explain?

  Hemant K Collette
  http://hemantoracledba.blogspot.com

• Change of primary key on the Table clears the other columns

  Preliminary info/Installation
  JDeveloper 11 g 11.1.1.6.0
  We have a table (object view or entity) that has 8 columns. The primary key is composed of 4 1 columns.
  The table is displayed in a page fragment.
  2 of the 4 non-primary key columns are LOV.
  All the 8 columns are needed.
  The table is editable including 2 of primary key columns.
  
  Question
  Assume that the table displays the 3 lines. If we change a rank 1 non-primary key column and a primary key in row 2 column, everything works well when we are committed to the database
  If, however, we first change a primary key column, then a primary key on a different line column, then the column/row primary key that changed us first, gets annihilated and the other columns LOV on this same line. The 2 columns that are not LOV keep data as it should. We then get a validation error because the required data are not present. All this happens before we try all commit to the database. If debug us and look the iterator, it has the old data in this document, before and after any performance on the binding.
  If we look at and update the data via the App Module, everything works well. We have tried to update the view, etc. through valueChangeListener also with no luck.

  If you change the primary key value, it should not be the primary key.

  This is true in the design of database relational regardless of how access you the data. In addition, EO don't like if you change the primary key value.

  Have you considered adding a surrogate key (use a sequence) and make your PK course a unique key?

  John

• How to check the account of a column value is less than the other value of column in a table with a single column

  Hello

  Please let me know how to query the table and get the records that are less than the other column.

  ID item_id item_type

  3     1           r1

  2 4 r2

  1 5 r3

  6 5 r4

  I need to get all the lines in which item_id < id

  o/p

  ID item_id item_type

  3     1           r1

  6 5 r4

  SELECT ID, ITEM_ID, ITEM_TYPE

  Of

  WHERE ITEM_ID<>

• Key Reg primary and foreign at the same table

  Hello
  
  It is - ok if create primary and foreign keys on the same table itself?
  
  For example:
  
  In a table X, I have two columns such as Codeunite and ParentUnitcode.
  Is it ok if create Mt10 as principal and ParentUnitcode as foreign keys in the table itself?
  
  The foreign key base table: OrganizationalUnit
  Foreign key columns: ParentUnitCode
  Primary/Unique key base: OrganizationalUnit
  Primary/unique key col: Mt10
  
  Can anyone answer me on that?
  
  Concerning
  Rajesh

  OWB,

  If the two tables are favouring a one-to-one relationship so there no need to have two separate tables and so you can have free referential foreign keys in the same table where the primary key.

• creating tables with references to foreign keys that are not created tables

  I have several patterns to create and each diagram has several tables that reference the columns in each other as a foreign key. So I have to sort out them in the order. In other words, if table A has the foreign key of the Table B column can create B first and then A. are there - it was none I can create a first and then B, that would save a lot of time.

  Hello

  ORA - aff wrote:

  I have several patterns to create and each diagram has several tables that reference the columns in each other as a foreign key. So I have to sort out them in the order. In other words, if table A has the foreign key of the Table B column can create B first and then A. are there - it was none I can create a first and then B, that would save a lot of time.

  You can create A without the constraints of foreign key and then, once the B array has been created, use ALTER TABLE to add the constraints of foreigners has.

• Identify the foreign key table

  I have a table that has a few constraints that are foreign keys to other tables (see column FK_ETHNIC below). My naming conventions are consistent so they all start with 'FK_ ". In SQL, how can I find the table that the foreign key column references? I have a process that must find this table and then get all of its columns.
  Thank you!
  
  CREATE TABLE STU_BASE
  (PK_ID VARCHAR2 (32), sys_guid() by default)
  CONSTRAINT pk_stu_base
  KEY ELEMENTARY SCHOOL
  With the HELP of INDEX TABLESPACE sis_express_index
  STORAGE (INITIAL 524288
  NEXT 524288
  PCTINCREASE 0),.
  STUDENT_ID VARCHAR2 (15).
  Fk_stu_base_ethnic FK_ETHNIC VARCHAR2 (32) CONSTRAINT
  REFERENCES
  Ethnic (PK_ID)
  REMOVE THE NULL VALUE;
  
  CREATE TABLE ETHNIC
  (PK_ID VARCHAR2 (32), sys_guid() by default)
  CONSTRAINT pk_ethnic
  KEY ELEMENTARY SCHOOL
  With the HELP of INDEX TABLESPACE sis_express_index
  STORAGE (4096 INITIAL
  NEXT 4096
  PCTINCREASE 0),.
  VARCHAR2 (2) ETHNIC,.
  ETHNIC_DESC VARCHAR2 (30),
  STATE_CODE VARCHAR2 (2),
  FEDERAL_CODE VARCHAR2 (2))

  You could do a self-join with CONSTRAINTS (USER, ALL, s/n) views. You can search a constrainttype of 'R' and you can attach it to itself based on the R_OWNER and R_CONSTRAINT_NAME columns.

  For example:

  SELECT r1.owner      AS child_owner
       , r1.table_name AS child_table
       , r2.owner      AS parent_owner
       , r2.table_name AS parent_table
  FROM   all_constraints r1
  JOIN   all_constraints r2 ON  r2.owner           = r1.r_owner
                            AND r2.constraint_name = r1.r_constraint_name
  WHERE  r1.constraint_type = 'R'
  ;
  

  Published by: Centinul on February 16, 2012 15:36