What is an advantage of placing computed expressions or derived columns inside an SQL view definition?

Difficulty: Easy

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

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