What Is Database Testing?

Database testing is the process of validating backend data stored in databases to ensure it is accurate, consistent, secure, and aligned with business rules. It focuses on verifying that data created through UI, APIs, or batch jobs is correctly stored, updated, retrieved, and deleted.

In large service-based organizations like Cognizant (popularly known as CTS), applications handle huge enterprise databases across banking, healthcare, insurance, and retail domains. Therefore, cts database testing interview questions are a key part of QA, manual testing, and automation testing interviews.

Why Database Testing Is Important in CTS Projects

• To validate UI/API vs database data
  
• To ensure business rules are enforced at DB level
  
• To prevent data duplication or data loss
  
• To maintain transaction accuracy and audit logs

Step-by-Step Database Testing Workflow

1. Understand Business Requirements

• What data is created or updated?
  
• Which fields are mandatory?
  
• What calculations are performed in DB?
  

2. Schema & Table Validation

• Table and column names
  
• Data types and field lengths
  
• Default values
  

3. Constraint Validation

• Primary Key
  
• Foreign Key
  
• NOT NULL
  
• UNIQUE
  

4. CRUD Validation

Operation	Purpose	SQL Used
Create	Insert data	INSERT
Read	Fetch data	SELECT
Update	Modify data	UPDATE
Delete	Remove data	DELETE

5. Advanced Database Validation

• Indexes (performance)
  
• Stored Procedures (business logic)
  
• Triggers (audit & logging)
  
• Transactions (commit/rollback)
  

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CTS Database Testing Interview Questions (100+ Q&A)

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Basic Database Testing Interview Questions (1–20)

1. What is database testing?

Database testing validates backend data using SQL queries to ensure accuracy and integrity.

2. Why is database testing important in CTS projects?

CTS works on enterprise-scale applications where incorrect data can lead to business or compliance issues.

3. What skills are required for database testing?

• SQL knowledge
  
• Understanding of database concepts
  
• Business logic understanding
  

4. What is CRUD?

• Create – INSERT
  
• Read – SELECT
  
• Update – UPDATE
  
• Delete – DELETE
  

5. What is a primary key?

A column that uniquely identifies each record.

6. What is a foreign key?

A column that creates a relationship between two tables.

7. What is data integrity?

Ensuring accuracy and consistency of data across tables.

8. What is normalization?

Reducing data redundancy.

9. What is denormalization?

Adding redundancy to improve performance.

10. What is a schema?

A logical container for database objects.

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SQL Interview Questions for Testing (21–45)

21. Fetch all records from a table

SELECT * FROM users;

22. Fetch users with age greater than 30

SELECT * FROM users WHERE age > 30;

23. Fetch unique city names

SELECT DISTINCT city FROM customers;

24. Sort records by created date

SELECT * FROM orders ORDER BY created_date DESC;

25. What is GROUP BY?

Groups rows with the same values.

SELECT department, COUNT(*)

FROM employees

GROUP BY department;

26. What is HAVING?

Filters grouped data.

SELECT department, COUNT(*)

FROM employees

GROUP BY department

HAVING COUNT(*) > 5;

27. Difference between WHERE and HAVING?

WHERE	HAVING
Filters rows	Filters grouped data
Used before GROUP BY	Used after GROUP BY

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JOIN-Based CTS Database Testing Interview Questions (46–65)

46. What is a JOIN?

Used to retrieve data from multiple tables.

47. Types of JOINs

• INNER JOIN
  
• LEFT JOIN
  
• RIGHT JOIN
  
• FULL JOIN
  

48. INNER JOIN example

SELECT o.order_id, c.name

FROM orders o

INNER JOIN customers c

ON o.customer_id = c.id;

49. LEFT JOIN use case

Find records without matching data.

SELECT c.name, o.order_id

FROM customers c

LEFT JOIN orders o

ON c.id = o.customer_id;

50. Scenario: Customers with no orders

SELECT c.id

FROM customers c

LEFT JOIN orders o

ON c.id = o.customer_id

WHERE o.id IS NULL;

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Indexes, Stored Procedures & Triggers (66–85)

66. What is an index?

Improves query performance by reducing table scans.

67. Types of indexes

• Clustered
  
• Non-clustered
  
• Composite
  

68. How do testers validate index usage?

By checking execution plans using EXPLAIN.

69. What is a stored procedure?

Pre-compiled SQL code stored in the database.

70. Stored procedure example

CREATE PROCEDURE getUser(IN uid INT)

BEGIN

  SELECT * FROM users WHERE id = uid;

END;

71. How do testers test stored procedures?

• Input validation
  
• Output verification
  
• Error handling
  

72. What is a trigger?

Automatically executes SQL on INSERT/UPDATE/DELETE.

73. Trigger example

CREATE TRIGGER audit_update

AFTER UPDATE ON orders

FOR EACH ROW

INSERT INTO audit_log VALUES (NEW.id, NOW());

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Scenario Based Database Testing Interview Questions (86–110)

86. Scenario: Validate user registration

• Record inserted
  
• Default values assigned
  

SELECT * FROM users WHERE email=’test@gmail.com’;

87. Scenario: Validate update operation

SELECT address FROM users WHERE id=101;

88. Scenario: Validate soft delete

SELECT * FROM users WHERE is_active=’N’;

89. Scenario: Detect duplicate records

SELECT email, COUNT(*)

FROM users

GROUP BY email

HAVING COUNT(*) > 1;

90. Scenario: Validate banking transaction

• Debit entry
  
• Credit entry
  
• Balance updated
  

SELECT balance FROM accounts WHERE acc_id=101;

91. Scenario: Validate rollback

• Force failure
  
• Ensure no partial data saved
  

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Advanced Database Testing Interview Questions (111–130)

111. What is a transaction?

A group of SQL statements executed as a single unit.

112. What are ACID properties?

• Atomicity
  
• Consistency
  
• Isolation
  
• Durability
  

113. What is a deadlock?

Two transactions waiting indefinitely for each other.

114. What is isolation level?

Controls visibility of uncommitted data.

115. What is data migration testing?

Validating data accuracy after migration.

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Real-Time Use Cases in CTS Projects

🏦 Banking

• Transaction accuracy
  
• Balance calculation
  
• Audit log validation
  

🏥 Healthcare

• Patient data integrity
  
• Medical history consistency
  
• Compliance checks
  

🛒 E-commerce

• Order vs payment reconciliation
  
• Inventory updates
  
• Refund processing validation
  

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Common Mistakes Testers Make

• Validating only UI data
  
• Ignoring NULL and default values
  
• Skipping rollback scenarios
  
• Missing negative test cases
  
• Not validating performance
  

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Quick Revision Sheet

✔ SELECT, WHERE, ORDER BY
✔ JOIN types
✔ GROUP BY, HAVING
✔ CRUD operations
✔ Index basics
✔ Stored procedures
✔ Triggers
✔ Transactions

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FAQs – CTS Database Testing Interview Questions

Q1. Is SQL mandatory for CTS database testing interviews?
Yes, SQL is a core skill for CTS testing roles.

Q2. Are scenario-based questions common?
Yes, scenario based database testing questions with answers are frequently asked.

Q3. Which databases are commonly used in CTS projects?
Oracle, MySQL, SQL Server, PostgreSQL.