Cognizant SQL Interview Questions 2026
Published July 22, 2026 · Updated July 22, 2026
5 real SQL interview questions asked at Cognizant. Upvoted by engineers who cleared the loop. Covers Technical rounds.
5 questions
82 engineers asked
129 upvotes
Company: Cognizant
Technology: SQL
All SQL Questions Asked at Cognizant
Cognizant
Easy
Technical round
0-3 yearsSQL
Explain the difference between INNER JOIN, LEFT JOIN, and FULL OUTER JOIN with a simple example of Orders and Customers tables.
↑ 30 upvotes · 22 engineers asked this · Developer
Cognizant
Medium
Technical round
2-5 yearsSQL
A SELECT query filtering on a non-indexed column takes 8 seconds on a 10 million row table. Would adding an index always help? What's the trade-off of adding too many indexes?
↑ 26 upvotes · 15 engineers asked this · Developer
Cognizant
Medium
Technical round
1-4 yearsSQL
What problem does database normalization (1NF, 2NF, 3NF) actually solve? Give an example of an update anomaly in an unnormalized table.
↑ 21 upvotes · 12 engineers asked this · Developer
Cognizant
Hard
Technical round
2-6 yearsSQL
Write a query to find, for each department, the employee with the second-highest salary, using window functions instead of a correlated subquery.
↑ 33 upvotes · 25 engineers asked this · Developer
Cognizant
Medium
Technical round
2-5 yearsSQL
How would you find out why a specific SQL query is slow before making any changes to it?
↑ 19 upvotes · 8 engineers asked this · Developer
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Frequently asked questions
Explain the difference between INNER JOIN, LEFT JOIN, and FULL OUTER JOIN with a simple example of Orders and Customers tables.
Explain the difference between INNER JOIN, LEFT JOIN, and FULL OUTER JOIN with a simple example of Orders and Customers tables.
A SELECT query filtering on a non-indexed column takes 8 seconds on a 10 million row table. Would adding an index always help? What's the trade-off of adding too many indexes?
A SELECT query filtering on a non-indexed column takes 8 seconds on a 10 million row table. Would adding an index always help? What's the trade-off of adding too many indexes?
What problem does database normalization (1NF, 2NF, 3NF) actually solve? Give an example of an update anomaly in an unnormalized table.
What problem does database normalization (1NF, 2NF, 3NF) actually solve? Give an example of an update anomaly in an unnormalized table.
Write a query to find, for each department, the employee with the second-highest salary, using window functions instead of a correlated subquery.
Write a query to find, for each department, the employee with the second-highest salary, using window functions instead of a correlated subquery.
How would you find out why a specific SQL query is slow before making any changes to it?
How would you find out why a specific SQL query is slow before making any changes to it?