# Cognizant Interview Questions with Answers

8 previously-asked interview questions from Cognizant's hiring process, each with the correct answer and a worked explanation. Written against the company's actual test pattern.

_Source: Astra (https://useastra.in). Updated 2026-09-05._

### 1. Why do you want to join Cognizant?

**Answer:** Tie Cognizant strengths such as strong digital and healthcare practice, structured GenC training and global client exposure to your goal of building a strong foundation and growing into specialised tech roles. Be specific and sincere.

### 2. What is the difference between DELETE, TRUNCATE and DROP in SQL?

**Answer:** DELETE removes selected rows and can be rolled back and filtered with WHERE. TRUNCATE removes all rows quickly, cannot use WHERE and usually cannot be rolled back. DROP removes the entire table structure and data.

### 3. Explain normalization and its main normal forms.

**Answer:** Normalization organises data to reduce redundancy and anomalies. 1NF removes repeating groups, 2NF removes partial dependency on a composite key, 3NF removes transitive dependency, and BCNF is a stricter 3NF.

### 4. What is polymorphism? Give an example.

**Answer:** Polymorphism lets one interface represent different underlying forms. Compile-time via overloading (same name, different parameters) and run-time via overriding (a subclass redefines a parent method). Example: a draw() method behaving differently for Circle and Square.

### 5. What is the difference between an array and a linked list?

**Answer:** An array stores elements contiguously with O(1) random access but costly insertions and a fixed size. A linked list stores nodes with pointers, allowing O(1) insertion or deletion given a node but only O(n) sequential access and extra memory for pointers.

### 6. Explain the difference between the GET and POST HTTP methods.

**Answer:** GET requests data and passes parameters in the URL, is cacheable and has length limits. POST sends data in the request body, is used to create or submit data, is not cached and is more suitable for sensitive or large payloads.

### 7. What is a deadlock and how can it be prevented?

**Answer:** A deadlock is a circular wait where processes hold resources and wait for others. It needs four conditions (mutual exclusion, hold and wait, no preemption, circular wait); breaking any one prevents it, for example by ordering resource requests or using timeouts.

### 8. What is the difference between an abstract class and an interface?

**Answer:** An abstract class can have both implemented and abstract methods and state, and a class extends only one. An interface (classically) declares method signatures a class must implement, and a class can implement many. Use an interface for a contract and an abstract class for shared partial behaviour.

More Cognizant preparation, including the full recruitment process: https://useastra.in/campus/cognizant