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CASCADE: This enables us to remove its all adopted records when parent is deleted. For example, we have removed blog record, its adopted comment records will be deleted.
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RESTRICT: This enables us to prevent deletion of record when it has a adopted record at least.
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These enable us to set data that we want into relation column of adopted records that we will remove its parent.
- SET NULL:
- SET DEFAULT:
- SET (...):
- NO ACTION: It does not anything. You should avoid choose this inside all of these choices.