Nielsen Interview Questions, Process, and Tips

Q1. SQL: Find the nth highest salary of employee?
Ans. 
Use SQL query with ORDER BY and LIMIT to find the nth highest salary of an employee.
• Use ORDER BY clause to sort salaries in descending order

• Use LIMIT to specify the nth highest salary

• Example: SELECT salary FROM employees ORDER BY salary DESC LIMIT n-1, 1
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Q2. SQL: Types of Joins in SQL?
Ans. 
Types of joins in SQL include INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL JOIN.
• INNER JOIN: Returns rows when there is at least one match in both tables.

• LEFT JOIN: Returns all rows from the left table and the matched rows from the right table.

• RIGHT JOIN: Returns all rows from the right table and the matched rows from the left table.

• FULL JOIN: Returns rows when there is a match in one of the tables.
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Q3. Algorithm: BinarySearch algorithm using Recursion, explanation and implementation.
Ans. 
BinarySearch algorithm using Recursion finds the target element in a sorted array by dividing the array in half at each step.
• Divide the array in half and compare the target element with the middle element

• If the target element is smaller, search the left half recursively

• If the target element is larger, search the right half recursively

• Repeat until the target element is found or the array is empty
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Q4. Given a string s and t find that s is a subsequence string in t or not?
Ans. 
Check if string s is a subsequence of string t.
• Iterate through both strings using two pointers.

• Compare characters of s and t, moving pointer in t only if characters match.

• If all characters of s are found in t in order, return true.

• Example: s = 'abc', t = 'ahbgdc' => true
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Q1. Basic Form Validation on React Js but on a platform which doesn't have syntax highlighting. Expected best coding standards to be followed.
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Q1. React Js and JavaScript questions
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Q1. Technical questions based on situations.
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I was asked to write SQL queries for 3rd highest salary of the employee, some name filtering, group by tasks.
Python code to find the index of the maximum number without using numpy.

Q1. Explain the Project undertaken during the research and follow-up questions
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Q1. Write pandas query to separate the names as first and last name from the full name. Drop the duplicate columns and also the missing values. Write output for the Python code. Write SQL query to retrieve t...read more
Ans. 
Answering questions related to data science concepts and techniques.
• Recall is the ratio of correctly predicted positive observations to the total actual positives. Precision is the ratio of correctly predicted positive observations to the total predicted positives.

• To reduce variance in an ensemble model, techniques like bagging, boosting, and stacking can be used. Bagging involves training multiple models on different ...read more
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Q1. Shallow copy and deep copy
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Q2. What is Pure component
Ans. 
A Pure component is a component in React that does not have any state or lifecycle methods, resulting in improved performance.
• Pure components are used to prevent unnecessary re-renders in React applications.

• Pure components implement shouldComponentUpdate method with shallow comparison of props and state.

• Examples of Pure components include functional components and class components that extend PureComponent class.
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