In SQL, which of the following is a reason for using a view to hide certain columns from users?

Introduction / Context:
SQL views are virtual tables defined by queries. They are powerful tools for simplifying complex queries, providing customized perspectives on data, and enforcing security policies. One common use case is to hide sensitive columns from specific users while still giving them access to other data. This question asks you to identify the best reason for using a view when the goal is to hide columns while also making query results easier to work with.

Given Data / Assumptions:

• A view is defined as a saved SQL query that presents data as a virtual table.
• Views can include or exclude columns from underlying base tables.
• There may be multiple motivations for using views, such as security and simplification.
• The question specifically mentions hiding columns and asks about related reasons.

Concept / Approach:
Views can serve multiple purposes at once. By defining a view that selects only certain columns, you can prevent users from seeing sensitive information such as salaries, passwords, or personal identification numbers. At the same time, a view can simplify complex joins or filter conditions, providing users with a clean and focused subset of the data. The best answer will acknowledge both the security and simplification benefits of using views rather than limiting the purpose to just one aspect.

Step-by-Step Solution:
Step 1: Recall that views can restrict access to specific columns by excluding them from the SELECT list.Step 2: Recognize that this helps in hiding sensitive data from certain users.Step 3: Also recall that views can encapsulate complex joins and conditions, resulting in simpler query results for users.Step 4: Examine the options and identify which one mentions both simplification and security.Step 5: Select option C as it accurately combines both key reasons for using views.

Verification / Alternative check:
To verify, imagine a payroll database where the base Employee table includes columns such as employee_id, name, department, and salary. You might create a view that only exposes employee_id, name, and department for general staff queries while hiding salary. At the same time, the view might hide complex joins by presenting a straightforward employee list. This shows that views can both hide sensitive columns and simplify query results, confirming that both motivations are valid and often used together.

Why Other Options Are Wrong:
Option A mentions only simplification and ignores the important security role of views in hiding sensitive columns. Option B mentions only preventing the display of sensitive data and ignores the simplification benefits. Option D claims that none of the listed reasons are valid, which is clearly false, because both simplification and security are widely recognized uses of views in SQL systems.

Common Pitfalls:
One pitfall is to think of views purely as security tools or purely as convenience tools, when in fact they often serve both roles. Another mistake is to assume that views alone are sufficient for security, while ignoring the need for proper access control on the underlying tables. A balanced understanding recognizes that views are a flexible mechanism that can simplify application logic and support fine grained access control when combined with proper privilege management.

Final Answer:
The best reason in this context is that views can be used To both simplify query results and hide sensitive columns from users, which is option C.