Foreign Key

I would like to create a foreign key but the Primary table has 2 fields as it Primary Key. Is there a way to create a Foreign Key that links only on one field of the primary key.

Ex: table 1: id int , language char(2), description varchar(100) PK = ID + language

table 2 : id int, idlanguage int PK = id FK (idLanguage refers to id from table 1)

This cause an error because the foreign key does not include all part of the primary key.

Rufen

If your table1.id is unique, then create primary key only on that column, if not, then you should add laguage in your table2 column because there will be no way to distinguish between languages that have the same id.
|||

I know that there will be no way to distinguish all records that have the same id, but that is what I want. When I delete a record from Table 1, I want to delete all record from table 2 that have this id (foreign from table 1).

|||

You can implement the foreign key logic using triggers.

For eg. For Delete

CREATE TRIGGER trg

ON table1

FOR DELETE

AS

BEGIN

DELETE FROM table2

WHERE idlanguage in (SELECT id FROM deleted)

END

You can have similar trigger for insert and update

foreign key

hi friends,
I want to check the relationship between tables before migration.
so i wrote a procedure which will push the unrelated data from the source
db(@.i_oldDB) to the error database(@.i_errorDb).
alter procedure TransactionValidation
(
@.i_oldDb varchar(100),
@.i_errorDb varchar(100),
@.i_ParentTable varchar(100),
@.i_ChildTable varchar(100),
@.i_PrimaryKey varchar(100),
@.i_ForeignKey varchar(100)
)
as
begin
Declare @.SQL nvarchar(4000)
select @.SQL = 'if exists (select * from ' + @.i_errorDb +
'.INFORMATION_SCHEMA.TABLES where ' +
'Table_Name like ' + CHAR(39) + @.i_ChildTable + CHAR(39) + ') drop table ' +
@.i_errorDb + '..'+ @.i_ChildTable
exec sp_executesql @.sql
select @.sql = 'SELECT * into ' + @.i_errorDb + '..' + @.i_ChildTable + ' from
'
+ @.i_oldDb + '..'+ @.i_ChildTable + ' where ' + @.i_oldDb + '..'+
@.i_ChildTable + '.' + @.i_ForeignKey + ' not in
(select ' + @.i_PrimaryKey + ' from ' + @.i_oldDb + '..'+ @.i_ParentTable + ')'
exec sp_executesql @.sql
select @.sql = 'delete from ' + @.i_oldDb + '..'+ @.i_ChildTable + ' where ' +
@.i_oldDb + '..'+ @.i_ChildTable + '.'
+ @.i_ForeignKey + ' not in
(select ' + @.i_PrimaryKey + ' from ' + @.i_oldDb + '..'+ @.i_ParentTable + ')'
exec sp_executesql @.sql
end
now my problem is, if i have multiple relationship column in the table...
this will not work. how to do this?
its very urgent.
pls help me to solve this.
thanks
vanithaThere are a couple of alternatives to NOT IN for composite keys. You could
use NOT EXISTS or an OUTER JOIN. The generated SQL would be something like
the untested examples below.
SELECT *
INTO MyErrorTable
FROM MyChildTable
WHERE NOT EXISTS
(
SELECT *
FROM MyParentTable
WHERE MyParentTable.Col1 = MyChildTable.Col1 AND
MyParentTable.Col2 = MyChildTable.Col2
)
SELECT MyChildTable.*
INTO MyErrorTable
FROM MyChildTable
LEFT OUTER JOIN MyParentTable ON
MyParentTable.Col1 = MyChildTable.Col1 AND
MyParentTable.Col2 = MyChildTable.Col2
WHERE MyParentTable.Col1 IS NULL
Hope this helps.
Dan Guzman
SQL Server MVP
"vanitha" <vanitha@.discussions.microsoft.com> wrote in message
news:710A7736-41F8-478F-BFFF-3AA86A31FFE0@.microsoft.com...
> hi friends,
> I want to check the relationship between tables before migration.
> so i wrote a procedure which will push the unrelated data from the source
> db(@.i_oldDB) to the error database(@.i_errorDb).
> alter procedure TransactionValidation
> (
> @.i_oldDb varchar(100),
> @.i_errorDb varchar(100),
> @.i_ParentTable varchar(100),
> @.i_ChildTable varchar(100),
> @.i_PrimaryKey varchar(100),
> @.i_ForeignKey varchar(100)
> )
> as
> begin
> Declare @.SQL nvarchar(4000)
> select @.SQL = 'if exists (select * from ' + @.i_errorDb +
> '.INFORMATION_SCHEMA.TABLES where ' +
> 'Table_Name like ' + CHAR(39) + @.i_ChildTable + CHAR(39) + ') drop table '
> +
> @.i_errorDb + '..'+ @.i_ChildTable
> exec sp_executesql @.sql
> select @.sql = 'SELECT * into ' + @.i_errorDb + '..' + @.i_ChildTable + '
> from
> '
> + @.i_oldDb + '..'+ @.i_ChildTable + ' where ' + @.i_oldDb + '..'+
> @.i_ChildTable + '.' + @.i_ForeignKey + ' not in
> (select ' + @.i_PrimaryKey + ' from ' + @.i_oldDb + '..'+ @.i_ParentTable +
> ')'
>
> exec sp_executesql @.sql
> select @.sql = 'delete from ' + @.i_oldDb + '..'+ @.i_ChildTable + ' where '
> +
> @.i_oldDb + '..'+ @.i_ChildTable + '.'
> + @.i_ForeignKey + ' not in
> (select ' + @.i_PrimaryKey + ' from ' + @.i_oldDb + '..'+ @.i_ParentTable +
> ')'
> exec sp_executesql @.sql
>
> end
> now my problem is, if i have multiple relationship column in the table...
> this will not work. how to do this?
> its very urgent.
> pls help me to solve this.
> thanks
> vanitha
>

Foreign key

Hello,
I need to add a column to a table. The new column is a foreign key which references another table's column.

how can you do this? Does it need to be done in two steps, like:

alter table table1
add new_col_name datatype

then

alter table table1
add table constraint.

If so, what is the syntax for adding a foreign key contraint which references another table.

thank youHello,

Yes, it has to be done in two steps, just as you said.

To add a foreign key constraint :

ALTER TABLE table1
ADD CONSTRAINT fk_table1_table2
FOREIGN KEY (field1)
REFERENCES table2(field2);
Where field1 is the column in table1 which is referenced by the column field2 in table2. If you have multi-column FK constraints, just put them in the right order, separated by commas :
ALTER TABLE table1
ADD CONSTRAINT fk_table1_table2
FOREIGN KEY (field11, field12)
REFERENCES table2(field21, field22);

Regards,

RBARAER|||thanks! what does the fk_table1_table2 mean? Is it just a lable?|||It can be done in one step, at least it can on Oracle:
alter table table1
add (new_col_name references table2(keycol));

or (to give the constraint a specific name):

alter table table1
add (new_col_name constraint table1_table2_fk references table2(keycol));|||cool, I'll try that also, but the first code worked.

foreign key

I want to make a foreign key relationship between two tables but the key is
multiple fields. I am getting an error message when I try.
'''''?Can you post DDL for your tables and the code you're trying to use to create
the foreign key constraint?
--
Adam Machanic
SQL Server MVP
http://www.sqljunkies.com/weblog/amachanic
--
"sql" <sql@.discussions.microsoft.com> wrote in message
news:186C8701-6A4E-4C68-81E7-29EB3A668400@.microsoft.com...
> I want to make a foreign key relationship between two tables but the key
is
> multiple fields. I am getting an error message when I try.
> '''''?|||ALTER TABLE SecondaryTableName
ADD CONSTRAINT ConstraintName
FOREIGN KEY (ForeignKeyColumns)
REFERENCES dbo.PrimaryTable (PrimaryKeyColumnName)
Be sure to list the composite columnc in the same order.
-Paul Nielsen, SQL Server MVP
SQL Server 2000 Bible, Wiley Press
Enterprise Data Architect, www.Compassion.com
"Adam Machanic" <amachanic@.hotmail._removetoemail_.com> wrote in message
news:%23S3OJUNyEHA.2788@.TK2MSFTNGP15.phx.gbl...
> Can you post DDL for your tables and the code you're trying to use to
> create
> the foreign key constraint?
> --
> Adam Machanic
> SQL Server MVP
> http://www.sqljunkies.com/weblog/amachanic
> --
>
> "sql" <sql@.discussions.microsoft.com> wrote in message
> news:186C8701-6A4E-4C68-81E7-29EB3A668400@.microsoft.com...
>> I want to make a foreign key relationship between two tables but the key
> is
>> multiple fields. I am getting an error message when I try.
>> '''''?
>|||Script and error message
ALTER TABLE MNP_MINE_PROD
ADD CONSTRAINT FK_TEST
FOREIGN KEY (MNE_ID, MOR_YEAR, ORT_ID)
REFERENCES MOR_MINE_OP_RPT (MNE_ID, MOR_YEAR, ORT_ID)
Server: Msg 547, Level 16, State 1, Line 1
ALTER TABLE statement conflicted with TABLE FOREIGN KEY constraint
'FK_TEST'. The conflict occurred in database 'S_DEV', table 'MOR_MINE_OP_RPT'.
"sql" wrote:
> I want to make a foreign key relationship between two tables but the key is
> multiple fields. I am getting an error message when I try.
> '''''?|||You have some rows in MNP_MINE_PROD that aren't in MOR_MINE_OP_RPT. So the
FK can't be created... try this:
SELECT *
FROM MNP_MINE_PROD A
WHERE NOT EXISTS
(SELECT *
FROM MOR_MINE_OP_RPT B
WHERE A.MNE_ID = B.MNE_ID
AND A.MOR_YEAR=B.MOR_YEAR
AND A.ORT_ID = B.ORT_ID)
Adam Machanic
SQL Server MVP
http://www.sqljunkies.com/weblog/amachanic
--
"sql" <sql@.discussions.microsoft.com> wrote in message
news:57509E6C-7118-4B0C-A0DF-B3EF4FCF9464@.microsoft.com...
> Script and error message
> ALTER TABLE MNP_MINE_PROD
> ADD CONSTRAINT FK_TEST
> FOREIGN KEY (MNE_ID, MOR_YEAR, ORT_ID)
> REFERENCES MOR_MINE_OP_RPT (MNE_ID, MOR_YEAR, ORT_ID)
> Server: Msg 547, Level 16, State 1, Line 1
> ALTER TABLE statement conflicted with TABLE FOREIGN KEY constraint
> 'FK_TEST'. The conflict occurred in database 'S_DEV', table
'MOR_MINE_OP_RPT'.
>
> "sql" wrote:
> > I want to make a foreign key relationship between two tables but the key
is
> > multiple fields. I am getting an error message when I try.
> > '''''?

Foreign key

How do I find out Foreign keys associated with a table?
How do I create Foreign Key when creating a table
using Enterprise manager.
Thank you,
Lin> How do I find out Foreign keys associated with a table?
http://www.aspfaq.com/2520
> How do I create Foreign Key when creating a table
> using Enterprise manager.
I recommend creating tables in Query Analyzer, then you can explicitly
declare foreign keys instead of using a GUI. See CREATE TABLE in Books
Online.
--
http://www.aspfaq.com/
(Reverse address to reply.)|||sp_help <table name> will show you the foreign keys associated with a give
table.
To add foreign key relationships in EM, click on the "Manage
Relationship..." toolbar item when creating a "New Table".
----
----
--
Need SQL Server Examples check out my website at
http://www.geocities.com/sqlserverexamples
"Lin" <anonymous@.discussions.microsoft.com> wrote in message
news:1bf2f01c4522f$18cc4fc0$a601280a@.phx.gbl...
> How do I find out Foreign keys associated with a table?
> How do I create Foreign Key when creating a table
> using Enterprise manager.
> Thank you,
> Lin
>|||Greg,
Thank you very much, this really helps!
-Lin
>--Original Message--
>sp_help <table name> will show you the foreign keys
associated with a give
>table.
>To add foreign key relationships in EM, click on
the "Manage
>Relationship..." toolbar item when creating a "New
Table".
>
>--
>----
--
>----
--
>--
>Need SQL Server Examples check out my website at
>http://www.geocities.com/sqlserverexamples
>"Lin" <anonymous@.discussions.microsoft.com> wrote in
message
>news:1bf2f01c4522f$18cc4fc0$a601280a@.phx.gbl...
>> How do I find out Foreign keys associated with a table?
>> How do I create Foreign Key when creating a table
>> using Enterprise manager.
>> Thank you,
>> Lin
>
>.
>|||Aaron,
Thank you very much!
-Lin
>--Original Message--
>> How do I find out Foreign keys associated with a table?
>http://www.aspfaq.com/2520
>> How do I create Foreign Key when creating a table
>> using Enterprise manager.
>I recommend creating tables in Query Analyzer, then you
can explicitly
>declare foreign keys instead of using a GUI. See CREATE
TABLE in Books
>Online.
>--
>http://www.aspfaq.com/
>(Reverse address to reply.)
>
>.
>sql

Foreign Key

Hi Friends,
Is there any way to get the table name which is referenced by the
foreign key

for example: consider two table "Staff" and "Department"

Staff with following columns
PK_ID
FK_DepartmentID
Name
Address

Department with following columns
PK_DepartmentID
DeptName

Actually what i need is: Initially i would be having the table name as
"Staff"
from Staff table i need to identify that the column FK_DepartmentID is
a foreign key
and the primary key is in the Department table

i need to traverse from Staff table and identify that FK_DepartmentID
is a primary key in Department table

this has to be accomplished by sql query... probably this could be
fetched from
Data Dictionary but i couldnt find the relationship between the system
tables.

Thanks
ArunDhaJArunDhaJ wrote:

Quote:

Originally Posted by

Hi Friends,
Is there any way to get the table name which is referenced by the
foreign key
(..)

(SQL Server 2005)

IMHO the easiest way is to use sys.foreign_keys. You don't need any
other system view. Try this:

USE YOUR_DATABASE; -- remember about current database context

SELECT
OBJECT_NAME(parent_object_id) as table_with_FK,
OBJECT_NAME(referenced_object_id) as referenced_table
FROM sys.foreign_keys
WHERE OBJECT_NAME(parent_object_id) = 'Staff'

--
Best regards,
Marcin Guzowski
http://guzowski.info

foreign key

Hi

is it a good practice to create FK on each & every column in a table whose values are taken from master table.

should I create or not.

If I create will that be heavy i.e what about memory consumption ?

pls reply

Thanks

Shubhangi1. You can foreign keys.

or

2. You can check through code. By using Inner join table name
on parenttabel.field=childtable.field

ro

3.Before inserting a record in child table, check whether it exists in the parent table through code by using if exists or if (select count(*) from tablename where
...)=0

or

if exists(select 1 from tablename where ...)