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I'm trying to use the Relationships dialog in SQL 2008 to add a new foreign key to a table field. When I go to add one, I am not able to change and specify the Foreign Key Base table or any others in the "Tables and Columns Specification" area...they'...
Answer Snippets (Read the full thread at stackoverflow):
ALTER TABLE dbo.MyTable ADD CONSTRAINT FK1_MyTable FOREIGN KEY(myNewColum) REFERENCES dbo.myRefTable(ID.
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I've created a table in MySQL:
CREATE TABLE actions ( A_id int NOT NULL AUTO_INCREMENT, type ENUM('rate','report','submit','edit','delete') NOT NULL, Q_id int NOT NULL, U_id int NOT NULL, date DATE NOT NULL, time TIME NOT NULL, rate tinyint(1), PRIMARY...
Started by stalepretzel on
, 4 posts
by 4 people.
Answer Snippets (Read the full thread at stackoverflow):
In MySQL, " KEY....
It silently accepts the declaration of a foreign key, but does not store the constraint or enforce for the foreign key.
I would guess that your default storage engine is MyISAM, which ignores foreign key constraints.
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I'm mapping a legacy database with nhibernate and having some problems with mapping a realation.
The two classes look like this
public class Questionnaire { public int Id {get; set;} public string FormCode {get; set;} public IList<Question> Questions...
Started by Colin G on
, 3 posts
by 3 people.
Answer Snippets (Read the full thread at stackoverflow):
Is ID.
But, as you're witnessing, that's not always the case.
foreign keys should be primary keys.
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I have the following tables:
Financial :
PK_FinancialID FK_SchoolID School :
PK_SchoolID Class :
PK_ClassID FK_SchoolID ClassName Both Class and Financial have Foreign Key relationships to School. I want to make a query that would show all classes that...
Started by Yaakov Ellis on
, 6 posts
by 6 people.
Answer Snippets (Read the full thread at stackoverflow):
As far as performance goes: I'm not really sure, but I'd say it would be faster because you have one less table to join - but I'm not an expert in that area.... .
Don't see anything wrong with that.
I'd say you're fine to leave out the actual school table .
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I have a Staff and e SecuredPage entity and the properties are below
Staff id Name LastName Level // SecuredPage.RoleId
SecuredPage id PageId RoleId // Staff.Level
I want to have a collection of SecuredPage in Staff entity, so it s a one-to-many but i...
Started by Barbaros Alp on
, 3 posts
by 3 people.
Answer Snippets (Read the full thread at stackoverflow):
I know this doesn't sound like what you wanted to hear (as you said you didn't create a Role entity) but you may want to consider... .
In reality, that is an expression of a many-to-many relationship .
I think the problem is that it's not really a one to many .
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I have a table T with a primary key id and foreign key f. Is f automatically indexed when it is specified as a foreign key? Do I need explicitly add an index for f ?
Started by Byron Whitlock on
, 4 posts
by 4 people.
Answer Snippets (Read the full thread at stackoverflow):
In SQL Server.
Questions/278982/are-foreign-keys-indexed-automatically-in-sql-server
Hi
In case of the foreign key constraint, the foreign key f in table T would be a primary key in the referenced table say T2.
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What is the name for the technique of using a set of foreign keys in a table where all but one are NULL for a given row?
In other words, each row needs a foreign key to one (and only one) of n different possible tables so you actually have all the necessary...
Started by James Tauber on
, 3 posts
by 3 people.
Answer Snippets (Read the full thread at stackoverflow):
Instead, I prefer to make one foreign for polymorphic associations:
Possible to do a MySQL foreign key to one of two possible tables? Referencing foreign keys in the same....
The term for the design you're describing is Exclusive Arc .
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How do I index a foreign key in Oracle?
Started by Ajay on
, 3 posts
by 3 people.
Answer Snippets (Read the full thread at stackoverflow):
You cannot index the foreign key constraint itself, but you can index the columns the foreign key is defined....
NOT NULL) ALTER TABLE mytable ADD CONSTRAINT fk_mytable_ref_reftable FOREIGN KEY (ref) REFERENCES it already has an index.
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Can i temporaryly disable a foreign key constraint. How do i do this?
Started by Vinodtiru on
, 4 posts
by 4 people.
Answer Snippets (Read the full thread at stackoverflow):
Using the default configuration....
To temporarily disable a constraint (foreign keys are constraints):
ALTER TABLE MyTable NOCHECK
Check also this related question:
Can foreign key constraints be temporarily disabled using TSQL into a table.
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As far as I know, foreign keys are used to aid the programmer to manipulate data in the correct way. Suppose a programmer is actually doing this in the right manner already, then do we really need the concept of foreign keys?
Are there any other uses ...
Started by Niyaz on
, 26 posts
by 25 people.
Answer Snippets (Read the full thread at stackoverflow):
I can't imagine....
Foreign keys can also help the programmer write less that point to that user.
They also improve performance because they're normally indexed by default .
Foreign keys help enforce referential integrity at the data level.
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