SQL Server Interview Topic 6: SQL in Backend APIs

This topic checks whether you can connect SQL Server knowledge to backend API work. Interviewers often ask how your C# or .NET API talks to the database.

🎯 Interview Goal

You should be able to explain how APIs read, filter, insert, update, and protect SQL Server data.

Q47. How does a backend API use SQL Server?

Quick interview answer:

A backend API receives a request, validates the input, talks to SQL Server, and returns a response. For example, an API endpoint like GET /students can read student rows from SQL Server and return them as JSON.

Study in detail: API Integration - This article explains how SQL Server connects to backend API work.

Q48. Why should we avoid building SQL by joining strings?

Quick interview answer:

Building SQL by joining strings can create SQL injection risk. A user may enter harmful text that changes the meaning of the query. We should use parameters so user input is treated as data, not as SQL code.

Study in detail: Security - This lesson explains safe database access and secure query habits.

Q49. What is a parameterized query?

Quick interview answer:

A parameterized query keeps SQL command text separate from user input values. It is safer and easier to maintain. For example, @StudentId is passed as a value instead of directly joining it into the SQL string.

Study in detail: Security - This article explains why parameters help protect data.

Q50. How do you handle search filters in SQL?

Quick interview answer:

Search filters use WHERE conditions based on user input. For example, a student search screen may filter by class, active status, or name. The query should handle optional filters carefully and should not return unnecessary rows.

Study in detail: Select and Where and API Integration - These lessons connect filtering with application screens.

Q51. What is pagination and why is it needed?

Quick interview answer:

Pagination returns data in small pages instead of sending all rows at once. It improves performance and user experience. For example, a student list API may return 20 students per page instead of 20,000 students in one response.

Study in detail: Performance Case Studies - This article explains performance thinking for real screens.

Q52. When would an API call a stored procedure?

Quick interview answer:

An API may call a stored procedure when the database operation is reusable, report-heavy, or contains multiple SQL steps. For simple CRUD, teams may use normal queries or an ORM. The decision depends on project standards and complexity.

Study in detail: Stored Procedures and Functions - This lesson explains stored procedure usage with examples.

Q53. What should an API return when SQL Server has no matching data?

Quick interview answer:

If the request is valid but no data exists, the API can return an empty list or a not found response depending on the endpoint. For example, a student list can return an empty array, but a single student detail by id can return 404.

Study in detail: API Integration - This article explains database results from an API point of view.

Practice Before Next Topic

Explain these API scenarios:

1. Student list with class filter and pagination.
2. Student details by StudentId.
3. Insert student using safe parameters.
4. Update student mobile number.
5. Return empty result when no records match.

💡 Beginner Interview Tip

In full stack interviews, connect SQL answers to screens and APIs. That makes your answer sound project-ready.