Thorsten have point us that WIKI page about this command looks strange, because uses
Referential_action
: NO ACTION (alias to RESTRICT)
| RESTRICT
| SET NULL
| SET DEFAULT
| CASCADE
Now SQL grammar have one more rule vext_referential_action_for_link without “SET NULL”, “SET DEFAULT” and added “NO CADCADE” for Binary Links.
Referential_action
: NO ACTION (alias to RESTRICT)
| RESTRICT
| CASCADE
| NO CASCADE
We have added “NO CASCADE”, because “NO ACTION” is used as RESTRICT by SQL Standard, SET NULL have no sense for Binary Link, because we do not have field to set its value to NULL, but we still need somehow say “do nothing with child records, when a parent record is deleted”. We decide that “NO CASCADE” is good choice, because
- no new keywords added
- similar to “NO ACTION” by syntax: two words via space char
- is obvious reverse to “CASCADE” action.
