What is an advantage of placing computed expressions or derived columns inside an SQL view definition?
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ATo save users from repeatedly writing the same expression
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BTo ensure that calculations are applied consistently for all consumers
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CBoth of the above
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DNone of the above — computations cannot appear in a view
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EOnly to improve physical storage size
Answer
Correct Answer: Both of the above
Explanation
Introduction / Context:Views can encapsulate business rules and computed values, providing a stable interface while underlying tables evolve. This reduces duplication and prevents errors.
Given Data / Assumptions:
- We want to reuse a calculation across many queries.
- We want uniform results for all consumers.
- We prefer centralizing logic in one definition point.
Concept / Approach:By placing expressions (e.g., price * quantity, tax calculations, standardized CASE logic) in a view, developers avoid rewriting them in every report or query. Centralization ensures consistent behavior and simplifies maintenance if the business rule changes—update the view once and all consumers benefit.
Step-by-Step Solution:
Identify repeated expression → move it into the view’s SELECT list as a derived column.Grant permissions on the view to expose the computed result while hiding raw columns if needed.Consumers select from the view, gaining both convenience and consistency.Verification / Alternative check:Compare codebases before/after: fewer duplicated expressions, reduced defect surface area, and simpler queries.
Why Other Options Are Wrong:Only one of the benefits: Ignores the other equally important advantage. Cannot appear in a view / storage size: Views are virtual; computations in the SELECT are fully supported and do not directly change physical storage.
Common Pitfalls:Complex computations in views can impact performance if not indexed properly (consider indexed/materialized views where supported and appropriate).
Final Answer:Both of the above