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Drop or Remove Foreign Key Constraint in SQL Server 2008

Nov 3, 2014
Introduction:

Here I will explain how to create or remove / drop foreign key constraint in
sql server.  Foreign key constraint in one table point to primary key in another table in sql serverand foreign key constraint is used to prevent the actions that would destroy the links between two tables.
Description:
In previous articles I explained Primary key constraint in sql server, foreign key constraint in sql server, Pass XML file as parameter from C# to SQL stored procedure, cursor example in sql server and many articles relating to SQL server. Now I will explain how to remove foreign key constraint in sql server.

Example of Foreign key constraint

Create one table with primary key and give name as UserDetails like as shown below

UserID
UserName
FirstName
LastName
     1
SureshDasari
Suresh
Dasari
     2
PrasanthiDonthi
Prasanthi
Donthi
     3
MaheshDasari
Mahesh
Dasari
After that create another table with Foreign Key and give name as SalaryDetails

SalID
Salary
UserID
     1
10000
1
     2
20000
2
     3
30000
3
The column “UserID” is a primary key in UserDetails table
The column “UserID” is a foreign key in SalaryDetails tables

If you observe above two tables UserID in “UserDetails” table points to UserID in “SalaryDetails”

Example of creating Foreign Key constraint during the time of table creation


Create Table SalaryDetails
(
SalaryID integer ,
Salary integer,
UserID varchar(50),
PRIMARY KEY (SalaryID),
CONSTRAINT fk_SalaryID FOREIGN KEY(UserID)
REFERENCES UserDetails(UserID)
)
Example of creating Foreign Key constraint during the time of ALTER TABLE


ALTER TABLE SalaryDetails ADD CONSTRAINT fk_SalaryID FOREIGN KEY (UserID) REFERENCES UserDetails(UserID)
To Drop Foreign Key constraint on table use the below statement


ALTER TABLE SampleUserDetail DROP Constraint fk_SalaryID

I hope it helps you….

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1 comments :

Sanket said...

Nice post

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