How to set the foreign key value as 'NULL'?

How to set the foreign key value as 'NULL'?



1.Using SET NULL and SET DEFAULT with Foreign Key ...

Description:Setting foreign key references to NULL is very easy to do with
SQL 2005 and above. ... it simply set all foreign key references to that
value to NULL.



2.FOREIGN KEY Constraints

Description:A FOREIGN KEY constraint can contain null ... the action will
fail when the deleted or changed primary key value corresponds to a value
in the FOREIGN KEY constraint ...



3.Foreign key - Wikipedia, the free encyclopedia

Description:... foreign key is a field (or ... SET NULL or SET DEFAULT is
the same for both ON DELETE or ON UPDATE: The value of the affected
referencing attributes is changed to ...



4.mysql - How to set the foreign key value as 'NULL ...

Description:How to set foreign key in table2 value as NULL when the
primary key in the table1 is deleted? I have created 2 tables Item and
order_item. Item(item_no(primary key ...



5.Data Integrity - Oracle Documentation

Description:... causing all rows in child tables with dependent foreign
key values to set those values to null. ... Allowed if the new foreign key
value still references a ...



6.Oracle/PLSQL: Foreign Keys with set null on delete

Description:A foreign key with set null on delete means that if a record
in the parent table is deleted, then the corresponding records in the
child table will have the foreign ...



7.ALTER TABLE statement - Oracle Documentation

Description:... [ CASCADE | RESTRICT ] DROP { PRIMARY KEY | FOREIGN KEY
... the default value of a column is NULL. ... TABLE SAMP.EMP_PHOTO ALTER
PHOTO_FORMAT SET DATA ...



8.sql server - set null value in a foreign key column ...

Description:If CityId is set to NULL, then the foreign key constraint will
not be checked, and all will be good. On the other hand, if CityId is 0
(say, because you've specified ...



9.Constraints

Description:No two rows in a table can have the same primary key value.
You cannot enter NULL ... foreign key value, except NULL, ... SET NULL
specifies that all rows with ...



10.SQL Server Foreign Key Update and Delete Rules

Description:A foreign key value may be NULL and indicates a particular
record ... Associated values in child table would be set to NULL. Foreign
key column should allow NULL ...