Oracle SQL Developer Interview Questions and Answers

Round duration - 120 Minutes
Round difficulty - Medium

The test included MCQ questions from SQL, Linux Commands, C/C++ programming, Logical Reasoning, Aptitude
questions. The other section was the coding round, where 2 SQL queries and 2 coding questions were there.

Q1. 
Pythagorean Triplets Detection
Determine if an array contains a Pythagorean triplet by checking whether there are three integers x, y, and z such that x² + y² = z² within the array.
Input:
The first lin...read more
Ans. 
Detect if an array contains a Pythagorean triplet by checking if there are three integers x, y, and z such that x^2 + y^2 = z^2.
• Iterate through all possible triplets of numbers in the array and check if they form a Pythagorean triplet.

• Use a nested loop to generate all possible combinations of three numbers from the array.

• Check if the sum of squares of any three numbers is equal to the square of another number.

• Return 'y...read more
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Q2. 
First Unique Character in a String Problem Statement
Given a string STR consisting of lowercase English letters, identify the first non-repeating character in the string and return it. If no such characte...read more
Ans. 
Identify the first non-repeating character in a string and return it, or '#' if none exists.
• Iterate through the string to count the frequency of each character

• Iterate through the string again to find the first character with frequency 1

• Return the first non-repeating character or '#' if none exists
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Round duration - 70 Minutes
Round difficulty - Medium

This was a standard DSA round where I was asked to solve 2 questions and also code it in a production ready manner . After DS and Algo , I was asked some questions from OOPS and Java followed by some Unix Commands and basic concepts from Operating Systems.

Q1. 
Find Duplicates in an Array
Given an array ARR of size 'N', where each integer is in the range from 0 to N - 1, identify all elements that appear more than once.
Return the duplicate elements in any orde...read more
Ans. 
Find duplicates in an array of integers within a specified range.
• Iterate through the array and keep track of the count of each element using a hashmap.

• Return elements with count greater than 1 as duplicates.

• Time complexity can be optimized to O(N) using a set to store duplicates.
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Q2. 
Reverse Linked List Problem Statement
Given a singly linked list of integers, return the head of the reversed linked list.
Example:
Initial linked list: 1 -> 2 -> 3 -> 4 -> NULL
Reversed link...read more
Ans. 
Reverse a singly linked list of integers and return the head of the reversed linked list.
• Iterate through the linked list and reverse the pointers to point to the previous node instead of the next node.

• Use three pointers - prev, current, and next to reverse the linked list in O(N) time and O(1) space complexity.

• Update the head of the reversed linked list as the last node encountered during the reversal process.
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Q3. What are Serialization and Deserialization in Java?
Ans. 
Serialization is the process of converting an object into a byte stream, while deserialization is the reverse process.
• Serialization is used to persist object state or transmit objects over a network.

• Deserialization reconstructs the object from the byte stream.

• Java provides Serializable interface for serialization and ObjectInputStream/ObjectOutputStream classes for deserialization.

• Example: Serializing an object to a fi
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Q4. Can you explain the Singleton Class in Java?
Ans. 
Singleton class in Java ensures that a class has only one instance and provides a global point of access to it.
• Singleton class restricts the instantiation of a class to one object.

• It provides a way to access its unique instance globally.

• Commonly implemented using a private constructor and a static method to return the instance.

• Example: Logger class in a multi-threaded application.
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Q5. Can you explain piping in Unix/Linux?
Ans. 
Piping in Unix/Linux allows the output of one command to be used as the input for another command.
• Piping is done using the | symbol

• It helps in connecting multiple commands together to perform complex operations

• Example: ls -l | grep .txt - This command lists all files in long format and then filters out only the .txt files
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Round duration - 30 Minutes
Round difficulty - Easy

This was a typical HR round with some standard Behavioral questions .

Q1. What is something about you that is not included in your resume?
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