How to create on delete Cascade triggers in SQL Server?
As SQL Server can refuse to create ON DELETE CASCADE constraints due to potential cycles, I decided to just indicate the FOREIGN KEY constraint and then have each table referencing t_parent create a FOR DELETE trigger, each performing the CASCADE or SET NULL operation on its own rows.
How to solve the SQL Server multiple cascade path issue?
To get around this error by creating the foreign key with DELETE NO ACTION, we would end up with orphan records in the GrandChild table every time a DELETE statement is issued against the Parent or Child2 tables. Instead of doing this we are going to create an INSTEAD OF trigger in place of the DELETE CASCADE option.
Can a cascade delete be cascaded to more than one table?
No, MS SQL Server doesn’t allow the deletion of a Primary Key or Unique Constraint to be cascaded to more than one table. Try setting it up and you get an error message. Cascade delete only works from 1 dimension table to 1 fact table. It doesn’t work from 1 dimension table to many fact tables.
Can you use instead of trigger in SQL Server?
One caveat when using an INSTEAD OF trigger is that you can’t have a table with both a DELETE CASCADE foreign key constraint and an INSTEAD OF trigger. If we try to create a trigger on the Child2 table as things are setup now we’ll get the following error.
How does the on delete Cascade referential action work?
The following are steps that demonstrate how the ON DELETE CASCADE referential action works. Step 1. Create the buildings table: Step 2. Create the rooms table: Notice that the ON DELETE CASCADE clause at the end of the foreign key constraint definition. Step 3. Insert rows into the buildings table: Step 4. Query data from the buildings table:
Which is an example of MySQL on delete Cascade?
Let’s take a look at an example of using MySQL ON DELETE CASCADE . Suppose that we have two tables: buildings and rooms . In this database model, each building has one or many rooms. However, each room belongs to one only one building. A room would not exist without a building.
How to control the timing of Cascade delete?
The exact timing of when cascading behaviors happen to tracked entities can be controlled using ChangeTracker.CascadeDeleteTiming and ChangeTracker.DeleteOrphansTiming. See Changing Foreign Keys and Navigations for more information.