Wissen Infotech SQL Database Administrator Interview Questions and Answers

Basic aptitude and coding questions

Q1. Technical discussion based on resume
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Q1. The questions were mainly asked on the internship projects nd the skills you have mentioned in resume.
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Round duration - 60 Minutes
Round difficulty - Medium

This round started with 1 DSA question related to Dynamic Programming and then the interviewer switched to questions revolving around fundamentals of Java and OOPS.

Q1. 
Count Ways to Reach the N-th Stair Problem Statement
You are provided with a number of stairs, and initially, you are located at the 0th stair. You need to reach the Nth stair, and you can climb one or tw...read more
Ans. 
The task is to determine the number of distinct ways to climb from the 0th to the Nth stair, where you can climb one or two steps at a time.
• Use dynamic programming to solve this problem efficiently.

• Define a recursive function to calculate the number of ways to reach each stair.

• Consider base cases for 0 and 1 stairs, and then use the recursive formula to calculate for N stairs.

• Use modulo 10^9+7 to handle large numbers a...read more
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Q2. What are the various access specifiers in Java?
Ans. 
Access specifiers in Java control the visibility of classes, methods, and variables.
• There are four access specifiers in Java: public, private, protected, and default.

• Public: accessible from any other class.

• Private: accessible only within the same class.

• Protected: accessible within the same package and subclasses.

• Default: accessible only within the same package.
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Q3. How many types of memory areas are allocated by the JVM?
Ans. 
JVM allocates 5 types of memory areas: Method Area, Heap, Stack, PC Register, and Native Method Stack.
• Method Area stores class structures, method data, and runtime constants.

• Heap is where objects are allocated and memory for new objects is dynamically allocated.

• Stack stores local variables and partial results, and each thread has its own stack.

• PC Register holds the address of the JVM instruction currently being execute...read more
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Q4. What do you mean by data encapsulation?
Ans. 
Data encapsulation is the concept of bundling data with the methods that operate on that data, restricting access to the data from outside the bundle.
• Data encapsulation is a fundamental principle of object-oriented programming.

• It allows for the data to be hidden and only accessed through the defined methods.

• Encapsulation helps in achieving data security and prevents accidental modification of data.

• Example: In a class r...read more
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Q5. Can static methods be overridden?
Ans. 
No, static methods cannot be overridden in Java.
• Static methods belong to the class itself, not to any specific instance of the class.

• Subclasses can have static methods with the same signature as the parent class, but they are not considered overridden.

• Example: Parent class has a static method 'display()', and subclass also has a static method 'display()'. These are two separate methods, not an override.
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Round duration - 60 Minutes
Round difficulty - Medium

In this round, the interviewer first started asking questions related to Java and Spring Boot and then he switched to Hibernate. The interview however ended with the interviewer asking me some basic queries related to SQL.

Q1. What is dependency injection?
Ans. 
Dependency injection is a design pattern where components are given their dependencies rather than creating them internally.
• Allows for easier testing by providing mock dependencies

• Promotes loose coupling between components

• Improves code reusability and maintainability

• Examples: Constructor injection, Setter injection, Interface injection
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Q2. What is the purpose of using @ComponentScan in class files?
Ans. 
@ComponentScan is used in class files to enable component scanning for Spring beans.
• Enables Spring to automatically detect and register Spring components (beans) within the specified package(s)

• Reduces the need for manual bean registration in configuration files

• Can specify base packages to scan for components, or use default behavior to scan the current package and its sub-packages
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Q3. Can we override or replace the embedded Tomcat server in Spring Boot?
Ans. 
Yes, we can override or replace the embedded Tomcat server in Spring Boot.
• Spring Boot allows for customization of embedded servers by excluding the default server dependency and adding a different server dependency.

• For example, to replace Tomcat with Jetty, exclude Tomcat and add Jetty dependencies in the pom.xml file.

• Configuration properties can also be used to customize the embedded server in Spring Boot applications
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Q4. What is the starter dependency of the Spring Boot module?
Ans. 
The starter dependency of the Spring Boot module is spring-boot-starter.
• The starter dependency provides a set of common dependencies for a specific type of application.

• It helps in reducing the configuration overhead and simplifies the setup process.

• For example, 'spring-boot-starter-web' includes dependencies for building web applications.
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Q5. What is Hibernate caching?
Ans. 
Hibernate caching is a mechanism used to improve the performance of applications by reducing the number of database queries.
• Hibernate caching stores frequently accessed data in memory to reduce the need for repeated database queries.

• There are different levels of caching in Hibernate, such as first-level cache and second-level cache.

• First-level cache is associated with the Session object and is enabled by default.

• Second...read more
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Q6. What are the concurrency strategies available in Hibernate?
Ans. 
Hibernate provides optimistic and pessimistic concurrency control strategies.
• Optimistic concurrency control: Uses versioning or timestamp to check for concurrent updates.

• Pessimistic concurrency control: Locks the database records to prevent concurrent updates.

• Examples: @Version annotation for optimistic concurrency, LockMode.UPGRADE for pessimistic concurrency.
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Round duration - 30 Minutes
Round difficulty - Easy

This is a cultural fitment testing round. HR was very frank and asked standard questions. Then we discussed about my
role.

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