在SQL Server 2014中删除，同时保持引用完整性

Question

My instructor has asked us to DELETE a row from a referenced table. The question is: Delete operator 4. Don't forget referential integrity, but do not delete any trips or vehicles.

I understand cascade delete and referential integrity but cannot wrap my mind around this. To clarify, I know that Cascade delete would allow for the removal of the operator but would also delete the trips. He does not want the trips or any other referencing table to change.

I though it might be a trick question and just make all the fields of Operator 4 Null but they require a value so that's a no go.

Operator 4 is referenced by a table named Runs. The Runs table is referenced by a table named Schedule. The Schedule table is referenced by a table named Trips.

How can I DELETE operator 4 while maintaining referential integrity or is there an angle I'm not looking at it from.

Thank you in advance.

Answer 1

如果FK col可为空，则可以将其设置为null并删除以前引用的记录。