Views: Is a “dynamic view” (ordinary SQL view) one whose contents are computed on demand when the view is referenced, rather than stored physically?
-
AApplies — standard views are virtual and materialize at query time
-
BDoes not apply — all views persist their data physically
-
CApplies only if the view has no joins
-
DApplies only in procedural SQL engines
Answer
Correct Answer: Applies — standard views are virtual and materialize at query time
Explanation
Introduction / Context:The question distinguishes ordinary (virtual) views from materialized views. Understanding this affects performance expectations and refresh strategies.
Given Data / Assumptions:
- Ordinary SQL views store only the definition (query), not the result set.
- Materialized views (or snapshots) store results and need refresh.
- Terminology “dynamic view” often refers to a virtual, on-demand view.
Concept / Approach:When you SELECT from a standard view, the DBMS expands it into the underlying query and executes it, producing results at that moment. No separate physical table holds the view’s data (unless specifically materialized).
Step-by-Step Solution:Interpret “contents materialize when referenced” as virtual evaluation.Recall the difference from materialized views.Conclude the statement is accurate for standard views.
Verification / Alternative check:Explain plans show the base tables accessed when selecting from a normal view.
Why Other Options Are Wrong:Not all views persist data; only materialized views do. Join usage does not change virtual vs. materialized nature.
Common Pitfalls:Expecting performance like a precomputed table; if you need persisted results, use materialized views and manage refresh.
Final Answer:Applies — standard views are virtual and materialize at query time