Podcast
Questions and Answers
What happens when the CASCADE action is applied during a deletion?
What happens when the CASCADE action is applied during a deletion?
- All elements that reference the deleted element are also deleted. (correct)
- Only the referenced element is deleted.
- The reference is updated to NULL for all related elements.
- Modification of the referenced element is not allowed.
Which action prevents any changes if there are existing references?
Which action prevents any changes if there are existing references?
- SET NULL
- CASCADE
- RESTRICT (correct)
- ALLOW
What is the effect of the SET NULL action when a referenced element is modified?
What is the effect of the SET NULL action when a referenced element is modified?
- The reference is updated with a default value.
- Modification is executed without updating references.
- Related references are set to NULL. (correct)
- The reference remains unchanged.
In the context of referential integrity constraints, which statement accurately describes RESTRICT?
In the context of referential integrity constraints, which statement accurately describes RESTRICT?
If a reference is found during an action, what does the CASCADE action do?
If a reference is found during an action, what does the CASCADE action do?
Flashcards
Referential Integrity
Referential Integrity
Ensures that data relationships between tables are maintained, preventing inconsistencies during database actions like deletion or modification.
RESTRICT Action
RESTRICT Action
When deleting or modifying a row, the action is prohibited if any other row references the row.
SET NULL Action
SET NULL Action
When deleting or modifying a row, the reference to the row is set to NULL.
CASCADE Action
CASCADE Action
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Referential Integrity Constraints
Referential Integrity Constraints
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Study Notes
Referential Integrity Constraints
- Possible actions:
- RESTRICT: If a reference is found, deletion or modification is forbidden.
- SET NULL: If a reference is found, deletion or modification will update the reference with the NULL value.
- CASCADE: If a reference is found, deleting or modifying an element will cause the same operation on elements that reference it.
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