sql server - Sql error on update : The UPDATE statement conflicted with the FOREIGN KEY constraint

Question

I have a table called patient_address, which reference a PK key in patient table. But if i try to run one of the following statements :

update patient set id_no='7008255601088' where id_no='8008255601089'
update patient_address set id_no='7008255601088' where id_no='8008255601089'

I get this error message:

"The UPDATE statement conflicted with the REFERENCE constraint "FK__patient_a__id_no__27C3E46E". The conflict occurred in database "PMS", table "dbo.patient_address", column 'id_no'." or "The UPDATE statement conflicted with the FOREIGN KEY constraint "FK__patient_a__id_no__27C3E46E". The conflict occurred in database "PMS", table "dbo.patient", column 'id_no'." .

Does any body know the possible cause ? Thanks.

Answer 1

This error is encountered when the primary key of a table is updated but it is referenced by a foreign key from another table and the update specific is set to No action. The No action is the default option.

If this is your case and No action is set on the update operation you can change the foreign-key definition to Cascade.

Right click your foreign key and select Modify. In the Foreign key relationships dialog under the INSERT and UPDATE specifics set the UPDATE rule on Cascade:

You can also set the rule using T-SQL:

ALTER TABLE YourTable
DROP Constraint Your_FK
GO

ALTER TABLE YourTable
ADD CONSTRAINT [New_FK_Constraint]
FOREIGN KEY (YourColumn) REFERENCES ReferencedTable(YourColumn)
ON DELETE CASCADE ON UPDATE CASCADE
GO 

Hope this helps