What is Foreign Key Indexes?
We have doubt in definition of "Foreign Key Indexe",
Please give us a clear definition.
Thanks in advance
Soheil
We have doubt in definition of "Foreign Key Indexe",
Please give us a clear definition.
Thanks in advance
Soheil
Similar Messages
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Nobody can help me? What is Foreign key indexes?
We have doubt in definition of "Foreign Key Indexe",
Please give us a clear definition.
Thanks in advance
SoheilWe have doubt in definition of "Foreign Key Indexe",
Please give us a clear definition.
Thanks in advance
Soheil -
Actually what is foreign key?
why we use it?Hi satya,
A relationship which can be defined between tables and must be explicitly defined at field level. Foreign keys are used to ensure the consistency of data. Data entered should be checked against existing data to ensure that there are now contradiction. While defining foreign key relationship cardinality has to be specified. Cardinality mentions how many dependent records or how referenced records are possible.
As i know when we define foriegn key in an value table then its is called as check table.but i dont have clear idea about value table and chech table i have confusion in my mind. Latest Answer : Value table is attached at the domain level. For the data element VBELN_VA, the domain VBELN has Value table as VBUK.When we try to make field VBELN (having data elment VBELN_VA) as foreign key is some other table (for eg in VBAP) then system proposes
thanks
trinadh
reward me if usefull -
New SQL Developer Data Modeler : name of attributes of foreign key
Hi,
with designer the name of column of foreign key was the " short name of entity/table master" + "_" + "the name of column attribute of the master table" .
Instead in the sql developer D.M. the system uses directly the name of the column/attribute of the master table and if the name exists in the slave table it uses a number to distinguish them .
So, if i have a table with short name gp and a primmary key id and a slave table with even a column id ,
with the D.M i'll have in the slave table a column named id2; in the designer instead the new column is gp_id .
Is possible to have the same behavior of designer even in the SQL Developer Data Modeler ?
Regards
Gianpaolo GilibertoHi Gianpaolo,
the columns of foreign keys are generated without the short name of master tablehow do you define that short name? Table and column have property "Abbreviation" - short name should be set there. You need also to set naming templates in "General Options>Naming Standard>Templates". Templates will be used when foreign key is created or you can apply them in Table dialog or for whole relational model using pop-up menu in the browser.
no foreign key index is generated on foreign key columns I assume, you want it for DDL generation only - this is controlled in "General Options>DDL"
Regards,
Philip -
I am running an SQL(CE) script to create a DB. All script commands succeed, but the DB get "broken" after creating the last costaint: after running the script, viewing table properties of Table2 and clicking on "Manage relations" gives the following error: Unable to create foreign key: InvalidArgument=Value of '0' is not valid for 'index'. Parameter name: index. Wondering what does that refer to...
Here it is the script. Please note that no error is thrown by running the following queries (even from code that passing the queries by hand, one-by-one to sql server management studio).
CREATE TABLE [table1] (
[id_rubrica] numeric(18,0) NOT NULL
, [id_campo] numeric(18,0) NOT NULL
, [nome] nvarchar(100) NOT NULL
GO
ALTER TABLE [table1] ADD PRIMARY KEY ([id_rubrica],[id_campo]);
GO
CREATE UNIQUE INDEX [UQ__m_campi] ON [table1] ([id_campo] Asc);
GO
CREATE TABLE [table2] (
[id_campo] numeric(18,0) NOT NULL
, [valore] nvarchar(4000) NOT NULL
GO
ALTER TABLE [table2] ADD PRIMARY KEY ([id_campo],[valore]);
GO
ALTER TABLE [table2] ADD CONSTRAINT [campo_valoriFissi] FOREIGN KEY ([id_campo]) REFERENCES [table1]([id_campo]);
GO
Sid (MCP - http://www.sugata.eu)I know this is kind of old post, but did this realy solved your problem?
I'm getting this same error message after adding a FK constraint via UI on VS2008 Server Explorer.
I can add the constraint with no errors, but the constraint is not created on the DataSet wizard (strongly typed datasets on Win CE 6) and when I click "Manage Relations" on the "Table Properties" this error pop out:
"InvalidArgument=Value or '0' is not valid for 'index'.
Parameter name: index"
Even after vreating my table with the relation in SQL the same occurs:
CREATE TABLE pedidosRastreios (
idPedidoRastreio INT NOT NULL IDENTITY PRIMARY KEY,
idPedido INT NOT NULL CONSTRAINT FK_pedidosRastreios_pedidos REFERENCES pedidos(idPedido) ON DELETE CASCADE,
codigo NVARCHAR(20) NOT NULL -
Publish: dropping index when it is used for foreign key constraint enforcement
Hi,
I'm trying to update a target schema from a reference database via Publish. Among the changes to apply, there's an index that needs to be dropped. Since it's linked to a foreign key constraint, it cannot be deleted unless the foreign key is temporarily dropped
(I saw somewhere that disabling the foreign key should be enough but it doesn't seem to work either).
Since there are other changes to be made on the same table, this foreign key also has to be dropped before the script can delete the table and re-create it. This part of the script is correctly generated. The problem is that this part appears after the 'DROP
INDEX' instruction.
So when generating the update script, SSDT tries to drop the index BEFORE dropping the foreign key. And I can't drop the foreign key in my custom pre-deployment script, otherwise the update script would fail when trying to delete it again.
Shouldn't SSDT be smart enough to drop the constraint before the index? Is it a bug or did I forget to set an option? If it's not a bug, what can I do apart from doing it manually?
Thank you for your helpHi Elsa,
That sounds like a bug. Could you please file a Connect issue for this at
https://connect.microsoft.com/SQLServer/feedback/CreateFeedback.aspx using the category "Developer Tools (SSDT, BIDS, etc.)"? We're trying to track all bugs through
Connect so that you can tell when we have fixed the issue and we can request more information.
A workaround for this issue might be to write a pre-deployment script for your project to drop the foreign key prior to deployment. A pre-deployment script can be added to your project by right-clicking on the
project in solution explorer and then clicking on Add > Script... and selecting Pre-Deployment Script from the list.
Thanks! -
Question on indexing foreign key for replicated table
Hi everybody,
I have 2 tables with following script
create table
parent(parent_id number(2) not null,
parent_name varchar(20),
constraint parent_pk primary key(parent_id))
create table child(child_id number(2) not null,
parent_id number(2) not null,
child_name varchar2(20),
constraint pk_child primary key(child_id,parent_id),
constraint fk_child foreign key (parent_id) references parenr(parent_id)
I want to replicate them and I know to replicate these 2 tables i should add them to my replication group, my question is that the child_id has foreign key so as below link says
http://dbataj.blogspot.com/2007/11/advance-replication-part-ii-master.html
I should put an index on the foreign key.What type of index should it be and is the following script correct for my purpose?
CREATE BITMAP
INDEX "fk_child"
ON child ("PARENT_ID")
TABLESPACE "USERS"
I would appreciate your help in advance.
MeryA bitmap index is almost certainly not the sort of index you'd want to create. You would normally want just a normal index, i.e.
CREATE INDEX fk_child
ON child( parent_id )on the master database just to support normal DML operations (otherwise, deleting a row from the parent table requires doing a full table scan on the child table to see if there are any orphaned child records).
If you are trying to set up a multi-master replication environment, you would also need to replicate this index, since you'll want to support basic DML on both nodes.
Justin -
Hello all,
I have on table with a foreign key.
When I do a select statement with a WHERE clause containing the Foreign key, the table is fully scanned.
Can I index the foreign key in this case, it's an integer value (from 1 to 100 values) ? What index should i use ?More info:
http://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:292016138754
http://tkyte.blogspot.com/2009/10/httpasktomoraclecomtkyteunindex.html -
Can we associate index with foreign key?
hello
i have searched and could not find the answer to the above;
i have a foreign key constraint on the tables; i added an index on that column as well;
however when i query the all_constraints, under index_name for this foreign constraint there is nothing; only when i have PK/UK i case see indexes associated with them;
will then oracle still associate my index with the FK constrained column? or i need to excplicity associate it with the foreign key column? if so, how to do that?
thx
rgdsHi,
UserMB wrote:
i have a foreign key constraint on the tables; i added an index on that column as well;It helps if you give a specific example, such as:
"I have a foreign key constraint, where emp.deptno references dept.deptno. (Deptno is the primary key of dept.) I created an index called emp_deptno_idx on emp.deptno as well."
however when i query the all_constraints, under index_name for this foreign constraint there is nothing; only when i have PK/UK i case see indexes associated with them;Not all indexes are associated with a constraint. In the example above, you wouldn't expect to see anything about the index emp_demptno_idx in all_constraints or in all_cons_columns.
will then oracle still associate my index with the FK constrained column? or i need to excplicity associate it with the foreign key column? if so, how to do that?In the situation above, Oracle will still use the index when the optimizer thinks it will help. You don't have to do anything else. -
Creation of Index for Primary & Foreign Key required?
hi,
i would like to find out if a column is defined as the primary key, do i need to create a separate index for it? or defining a primary key will tell the db to automatically create an index for it?
does foreign key have the same behavior as the primary key constraint?
thanks!i would like to find out if a column is defined as the primary key, do i need to create a separate index for it? No
or defining a primary key will tell the db to automatically create an index for it? Yes
See
http://download-uk.oracle.com/docs/cd/B10501_01/appdev.920/a96590/adg05itg.htm#7265
does foreign key have the same behavior as the primary key constraint?No. See http://download-uk.oracle.com/docs/cd/B10501_01/appdev.920/a96590/adg05itg.htm#1574 -
Storage for Foreign Keys and Function based indexes
This may well be the silliest question of the day, but is it possible to specify the storage for a Foreign key or a function based index? I'm not even sure that it would make sense.
Well, a foreign key constraint is not a segment, nor is any other type of constraint. However, a function-based index is a segment, just like any other index. So, in that case, specify a tablespace, just like you would with any other index.
Something like this:
create index my_fbi on my_tab(upper(last_name)) tablespace my_index_tablespace;
-Mark
Message was edited by:
mbobak
Fixed minor typo. -
Hello there,
Should i index all foreign keys in the table if there are more then 20 foreign keys
please reply ASAP.If there is DML activity on the related parent tables you need to. Because updating the parent table causes the child table to be locked if there is no index on the foreign key.
By the way, if you need ASAP answers, do not use this forum or start paying to the respondents. -
In our table:
Table Name:
STATUS
Columns:
STATUSID NUMBER (PKEY)
USERID NUMBER (FKEY)
PATIENTNAME VARCHAR(30)
STATUS_DATE DATE
CREATE_DATE DATE
CHSTATUS VARCHAR(30)
PAYER_STATUS VARCHAR(30)
CHARGE_AMOUNT DOUBLE
INS_AMOUNT DOUBLE
X12IN CLOB
We have a foreign key on the USERID column. And this column appears in the WHERE clause always.
I wanted to know in addition to the foriegn key constraint, putting an INDEX on the USERID column will help query performance?
Generally speaking:
I wanted to know whether in oracle putting a foreign key constraint on a column creates an INDEX automatically or do I put the index specifically besides the FOREIGN key.
Thanks in Advance,
Rumpa GiriHello
Oracle does NOT create an index when you put a foreign key constraint on a column, so you need to create one if you want one.
Have a look at this discussion on asktom to understand when and why indexes on foreign keys are a good idea.
If your query that uses USERID in the where caluse returns a small number of rows in proportion to the number of rows in the table, adding an index could well help with query performance....but as always, it's best to benchmark it and get some stats that you can then use to make an informed choice.
HTH
David
Message was edited by:
david_tyler -
What is the advantage of Foreign keys in database
suppose if we do not have FK then what kind of advantage we could not avail. we can fetch data from two table by creating a relation in sql.....then why FK is required. thanks
Hi Mou_kolkata
Overall foreign keys are very useful for maintaining data integrity.
A nice article written by Armando
Prato at mssqltips.com explains
about importance of FKs.
Advantages and disadvantages of using Foreign keys was also discussed under the design section of msdn forums at.
SQL Server > Database Design.
Hope they are helpful.
Thanks and Regards, Ibrahim Mehdi. MCSE-DataPlatform -
What's the privileges to create foreign key to a different schema.table ?
Hi
In my current schema I want to add a new foreign key. But this key is referencing to a table in a different schema, like this:
Alter table some_table ADD ( Constraint FK_01 Foreign Key (L_ID) References schema.table (LL_ID));
and getting the error - ORA-01031 insufficient privileges
Which privileges do I need for this (At this time, I have only GRANT Select)? Any help would be much appreciated
Best regards
RemoHi,
You need GRANT REFERENCES object privilege to the user.
Cheers
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