-634 THE DELETE RULE MUST NOT BE CASCADE
Explanation
The code is used to report that the CASCADE delete
rule specified in the FOREIGN KEY clause of an ALTER TABLE statement
is invalid because:
- The relationship would form a cycle that would cause a table to be delete-connected to itself.
- The relationship would cause another table to be delete-connected to the same table through multiple paths with different delete rules or with a delete rule equal to SET NULL.
System action
The statement cannot be processed.
Programmer response
Change the delete rule.
SQLSTATE
42915