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What happens when you delete a foreign key?
A foreign key with cascade delete means that if a record in the parent table is deleted, then the corresponding records in the child table will automatically be deleted. A foreign key with cascade delete can be created using either a CREATE TABLE statement or an ALTER TABLE statement.
Can foreign keys handle deletes and updates?
Foreign keys cannot handle deletes and updates.
Can a foreign key be deleted?
You can delete a foreign key constraint in SQL Server by using SQL Server Management Studio or Transact-SQL. Deleting a foreign key constraint removes the requirement to enforce referential integrity.
Can a foreign key be updated?
No the foreign key is not updated automatically. You need to update the foreign key in the tables in which it is referenced by yourself else it would result in referential integrity exception. For updating the foreign key automatically you may use TRIGGERS.
Why are foreign key constraints important in SQL Server?
Foreign key constraints are an integral part of SQL Server database design. These are used to maintain integrity among related data in different tables. While implementing update and delete operations on values in the parent table (referenced table with primary key) we have to consider the impact on related values in the child table.
What happens when foreign key is set to null?
The data in child table (EmpEducation) shows that as a result of the update and delete operations foreign key values are set to NULL as shown below. For utilizing the SET DEFAULT rule for update/delete operations default value should be there for foreign key column. Else SET DEFAULT specification would fail by generating error message.
Is it safe to use default foreign key no action?
It’s good to have full understanding of these rules, but keeping the default rule NO ACTION and using scripts to first operate on foreign key values and then primary keys is a safer option. To avoid unexpected results comprehensive testing should be performed before using these rules for a given situation.
What’s the default rule for foreign key update?
Analyze your tables and create proper foreign key relations where they are missing. It’s good to have full understanding of these rules, but keeping the default rule NO ACTION and using scripts to first operate on foreign key values and then primary keys is a safer option.