![]() These are called, directly from the SQL:2011 spec There are five options for ON DELETE and ON UPDATE that can apply to the FOREIGN KEY. The foreign key constraint, the operation will fail. For example, if anĪction specifies SET DEFAULT but the default value would not satisfy Not excuse you from observing any constraints. Respectively, when the referenced row is deleted. Referencing row(s) to be set to nulls or their default values, These cause the referencing column(s) in the There are two other options: SET NULLĪnd SET DEFAULT. Referenced row is deleted, row(s) referencing it should beĪutomatically deleted as well. Transaction, whereas RESTRICT does not.) CASCADE specifies that when a NO ACTION allows the check to be deferred until later in the (The essential difference between these two choices is that If any referencing rows still exist when the constraint is checked, anĮrror is raised this is the default behavior if you do not specifyĪnything. RESTRICT prevents deletion of a referenced row. Restricting and cascading deletes are the two most common options. Cascading deletes is one thing you can do. To maintain data integrity, you have to do something to the "child" table. When you delete a row from the "parent" table-from "that_table"-you remove a valid value from the possible values for the "child" table. One way to interpret a foreign key declaration is, "All valid values for this column come from 'that_column' in 'that_table'." When you delete a row in the "child" table, nobody cares. it could mean delete the Parent record when the Child record isĭeleted, or it could mean delete the Child record when the Parent is So it goes with the foreign key declaration. ON DELETE CASCADE is an optional clause in a foreign key declaration. Records are owned by Parent records, which table needs the ON DELETE You should be able to work from that to make only the changes that you want in your database.For example, if I have two tables - Parent and Child - where Child This code will drop and create ALL FK constraints in a database. You can select from that table to get all the information you need.Ī post from John Paul Cook can be found here: This takes a bit of effort, but would result in your constraint being properly set for your case.ĮDIT 2: The information that you need is found in sys.foreign_keys. ALTER TABLE again to create the ON UPDATE CASCADE constraint for the FK in question. ![]() ALTER TABLE to drop the existing FK constraint.It is necessary to iterate through each table that has a FK constraint to the PK table. SQL Server does not support altering the constraints to a new setting. If you do not have the ON UPDATE CASCADE constraint, then you will need create scripts to complete the update.ĮDIT: Since you do not have the ON UPDATE CASCADE constraint, but you want to have that set up, it is a bit of work. If you have defined the Foreign Key constraints as ON UPDATE CASCADE then the Primary Key value that was changed should cascade down to all the Foreign Keys with that constraint. To generate the DROP foreign keys script, modify value to be equal to 'DROP' in the declaration clause : DECLARE char(6) = 'DROP' ![]() + ' ON DELETE ' + CASE 0 THEN 'NO ACTION ' SET = ' ON UPDATE ' + CASE 0 THEN 'NO ACTION ' SET = + = + NEXT FROM ColumnCursor INTO ColumnCursor Where fkc.constraint_object_id = by fkc.constraint_column_id On fk.object_id = fkc.constraint_object_id , COL_NAME(fk.referenced_object_id, fkc.referenced_column_id) Select COL_NAME(fk.parent_object_id, fkc.parent_column_id) ![]() , delete_referential_action, update_referential_action, OBJECT_SCHEMA_NAME(referenced_object_id)įETCH NEXT FROM FKcursor INTO = 0 , is_disabled, is_not_for_replication, is_not_trusted ![]() , OBJECT_NAME(parent_object_id), name, OBJECT_NAME(referenced_object_id) Select OBJECT_SCHEMA_NAME(parent_object_id) In order to script out creation or dropping of all foreign keys in your schema run the following script (taken from here) DECLARE sysname How can I update the foreign keys to make them ON CASCADE UPDATE ? Thus NO ACTION is taken after updating my primary keys columns. , I see that update_referential_action is set to 0. When I run followinq query select * from sys.foreign_keys where referenced_object_id=OBJECT_ID('myTable') Is it possible to update a primary key column value with cascading the update among all the foreign keys referencing it ? ![]()
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