In SQL, the referential action ON UPDATE CASCADE ensures which property of relational databases?
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ANormalization
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BData Integrity
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CMaterialized Views
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DAll of the above.
Answer
Correct Answer: Data Integrity
Explanation
Introduction / Context:Referential actions define how updates/deletes to parent rows propagate to child rows. Understanding ON UPDATE CASCADE is important for preserving relationships automatically.
Given Data / Assumptions:
- A foreign key constraint exists between parent and child tables.
- Parent key value may be updated.
- ON UPDATE CASCADE is enabled.
Concept / Approach:ON UPDATE CASCADE ensures that when a parent key is changed, all corresponding child rows are updated automatically to the new value. This maintains referential integrity.
Step-by-Step Solution:
Parent table key is updated.Without cascade, children would reference old, invalid key.Cascade updates child foreign keys, preserving integrity.Verification / Alternative check:SQL standard documents and DBMS manuals all define CASCADE actions as preserving referential integrity.
Why Other Options Are Wrong:Normalization: A design process, unrelated to runtime cascades. Materialized views: A query storage technique, unrelated. All of the above: Incorrect since only data integrity applies.
Common Pitfalls:Confusing CASCADE with triggers or assuming it normalizes data.
Final Answer:Data Integrity